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ladybird/Userland/Libraries/LibSoftGPU/Device.cpp
Jelle Raaijmakers 1a3af23a10 LibGL: Defer depth writing until after alpha testing 
In the OpenGL fixed function pipeline, alpha testing should happen
before depth testing and writing. Since the tests are basically boolean
ANDs, we can reorder them however we like to improve performance and as
such, we perform early depth testing and delay the more expensive alpha
testing until we know which pixels to test.

However, we were already writing to the depth buffer during the depth
test, even if the alpha test fails later on. Depth writing should only
happen if depth testing _and_ writing is enabled.

This change introduces depth staging, deferring the depth write until
we are absolutely sure we should do so.
2021-12-30 14:24:29 +01:00

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/*
* Copyright (c) 2021, Stephan Unverwerth <s.unverwerth@serenityos.org>
* Copyright (c) 2021, Jesse Buhagiar <jooster669@gmail.com>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Function.h>
#include <LibGfx/Painter.h>
#include <LibGfx/Vector2.h>
#include <LibGfx/Vector3.h>
#include <LibSoftGPU/Device.h>
namespace SoftGPU {
using IntVector2 = Gfx::Vector2<int>;
using IntVector3 = Gfx::Vector3<int>;
static constexpr int RASTERIZER_BLOCK_SIZE = 8;
constexpr static int edge_function(const IntVector2& a, const IntVector2& b, const IntVector2& c)
{
return ((c.x() - a.x()) * (b.y() - a.y()) - (c.y() - a.y()) * (b.x() - a.x()));
}
template<typename T>
constexpr static T interpolate(const T& v0, const T& v1, const T& v2, const FloatVector3& barycentric_coords)
{
return v0 * barycentric_coords.x() + v1 * barycentric_coords.y() + v2 * barycentric_coords.z();
}
template<typename T>
constexpr static T mix(const T& x, const T& y, float interp)
{
return x * (1 - interp) + y * interp;
}
ALWAYS_INLINE constexpr static Gfx::RGBA32 to_rgba32(const FloatVector4& v)
{
auto clamped = v.clamped(0, 1);
u8 r = clamped.x() * 255;
u8 g = clamped.y() * 255;
u8 b = clamped.z() * 255;
u8 a = clamped.w() * 255;
return a << 24 | r << 16 | g << 8 | b;
}
static FloatVector4 to_vec4(Gfx::RGBA32 rgba)
{
return {
((rgba >> 16) & 0xff) / 255.0f,
((rgba >> 8) & 0xff) / 255.0f,
(rgba & 0xff) / 255.0f,
((rgba >> 24) & 0xff) / 255.0f
};
}
static Gfx::IntRect scissor_box_to_window_coordinates(Gfx::IntRect const& scissor_box, Gfx::IntRect const& window_rect)
{
return scissor_box.translated(0, window_rect.height() - 2 * scissor_box.y() - scissor_box.height());
}
static constexpr void setup_blend_factors(BlendFactor mode, FloatVector4& constant, float& src_alpha, float& dst_alpha, float& src_color, float& dst_color)
{
constant = { 0.0f, 0.0f, 0.0f, 0.0f };
src_alpha = 0;
dst_alpha = 0;
src_color = 0;
dst_color = 0;
switch (mode) {
case BlendFactor::Zero:
break;
case BlendFactor::One:
constant = { 1.0f, 1.0f, 1.0f, 1.0f };
break;
case BlendFactor::SrcColor:
src_color = 1;
break;
case BlendFactor::OneMinusSrcColor:
constant = { 1.0f, 1.0f, 1.0f, 1.0f };
src_color = -1;
break;
case BlendFactor::SrcAlpha:
src_alpha = 1;
break;
case BlendFactor::OneMinusSrcAlpha:
constant = { 1.0f, 1.0f, 1.0f, 1.0f };
src_alpha = -1;
break;
case BlendFactor::DstAlpha:
dst_alpha = 1;
break;
case BlendFactor::OneMinusDstAlpha:
constant = { 1.0f, 1.0f, 1.0f, 1.0f };
dst_alpha = -1;
break;
case BlendFactor::DstColor:
dst_color = 1;
break;
case BlendFactor::OneMinusDstColor:
constant = { 1.0f, 1.0f, 1.0f, 1.0f };
dst_color = -1;
break;
case BlendFactor::SrcAlphaSaturate:
// FIXME: How do we implement this?
break;
default:
VERIFY_NOT_REACHED();
}
}
template<typename PS>
static void rasterize_triangle(const RasterizerOptions& options, Gfx::Bitmap& render_target, DepthBuffer& depth_buffer, const Triangle& triangle, PS pixel_shader)
{
// Since the algorithm is based on blocks of uniform size, we need
// to ensure that our render_target size is actually a multiple of the block size
VERIFY((render_target.width() % RASTERIZER_BLOCK_SIZE) == 0);
VERIFY((render_target.height() % RASTERIZER_BLOCK_SIZE) == 0);
// Return if alpha testing is a no-op
if (options.enable_alpha_test && options.alpha_test_func == AlphaTestFunction::Never)
return;
// Calculate area of the triangle for later tests
IntVector2 v0 { (int)triangle.vertices[0].position.x(), (int)triangle.vertices[0].position.y() };
IntVector2 v1 { (int)triangle.vertices[1].position.x(), (int)triangle.vertices[1].position.y() };
IntVector2 v2 { (int)triangle.vertices[2].position.x(), (int)triangle.vertices[2].position.y() };
int area = edge_function(v0, v1, v2);
if (area == 0)
return;
float one_over_area = 1.0f / area;
FloatVector4 src_constant {};
float src_factor_src_alpha = 0;
float src_factor_dst_alpha = 0;
float src_factor_src_color = 0;
float src_factor_dst_color = 0;
FloatVector4 dst_constant {};
float dst_factor_src_alpha = 0;
float dst_factor_dst_alpha = 0;
float dst_factor_src_color = 0;
float dst_factor_dst_color = 0;
if (options.enable_blending) {
setup_blend_factors(
options.blend_source_factor,
src_constant,
src_factor_src_alpha,
src_factor_dst_alpha,
src_factor_src_color,
src_factor_dst_color);
setup_blend_factors(
options.blend_destination_factor,
dst_constant,
dst_factor_src_alpha,
dst_factor_dst_alpha,
dst_factor_src_color,
dst_factor_dst_color);
}
// Obey top-left rule:
// This sets up "zero" for later pixel coverage tests.
// Depending on where on the triangle the edge is located
// it is either tested against 0 or 1, effectively
// turning "< 0" into "<= 0"
IntVector3 zero { 1, 1, 1 };
if (v1.y() > v0.y() || (v1.y() == v0.y() && v1.x() < v0.x()))
zero.set_z(0);
if (v2.y() > v1.y() || (v2.y() == v1.y() && v2.x() < v1.x()))
zero.set_x(0);
if (v0.y() > v2.y() || (v0.y() == v2.y() && v0.x() < v2.x()))
zero.set_y(0);
// This function calculates the 3 edge values for the pixel relative to the triangle.
auto calculate_edge_values = [v0, v1, v2](const IntVector2& p) -> IntVector3 {
return {
edge_function(v1, v2, p),
edge_function(v2, v0, p),
edge_function(v0, v1, p),
};
};
// This function tests whether a point as identified by its 3 edge values lies within the triangle
auto test_point = [zero](const IntVector3& edges) -> bool {
return edges.x() >= zero.x()
&& edges.y() >= zero.y()
&& edges.z() >= zero.z();
};
// Calculate block-based bounds
auto render_bounds = render_target.rect();
if (options.scissor_enabled)
render_bounds.intersect(scissor_box_to_window_coordinates(options.scissor_box, render_target.rect()));
int const block_padding = RASTERIZER_BLOCK_SIZE - 1;
// clang-format off
int const bx0 = max(render_bounds.left(), min(min(v0.x(), v1.x()), v2.x())) / RASTERIZER_BLOCK_SIZE;
int const bx1 = (min(render_bounds.right(), max(max(v0.x(), v1.x()), v2.x())) + block_padding) / RASTERIZER_BLOCK_SIZE;
int const by0 = max(render_bounds.top(), min(min(v0.y(), v1.y()), v2.y())) / RASTERIZER_BLOCK_SIZE;
int const by1 = (min(render_bounds.bottom(), max(max(v0.y(), v1.y()), v2.y())) + block_padding) / RASTERIZER_BLOCK_SIZE;
// clang-format on
u8 pixel_mask[RASTERIZER_BLOCK_SIZE];
static_assert(RASTERIZER_BLOCK_SIZE <= sizeof(decltype(*pixel_mask)) * 8, "RASTERIZER_BLOCK_SIZE must be smaller than the pixel_mask's width in bits");
FloatVector4 pixel_staging[RASTERIZER_BLOCK_SIZE][RASTERIZER_BLOCK_SIZE];
float depth_staging[RASTERIZER_BLOCK_SIZE][RASTERIZER_BLOCK_SIZE];
// FIXME: implement stencil testing
// Iterate over all blocks within the bounds of the triangle
for (int by = by0; by < by1; by++) {
for (int bx = bx0; bx < bx1; bx++) {
// Edge values of the 4 block corners
// clang-format off
auto b0 = calculate_edge_values({ bx * RASTERIZER_BLOCK_SIZE, by * RASTERIZER_BLOCK_SIZE });
auto b1 = calculate_edge_values({ bx * RASTERIZER_BLOCK_SIZE + RASTERIZER_BLOCK_SIZE, by * RASTERIZER_BLOCK_SIZE });
auto b2 = calculate_edge_values({ bx * RASTERIZER_BLOCK_SIZE, by * RASTERIZER_BLOCK_SIZE + RASTERIZER_BLOCK_SIZE });
auto b3 = calculate_edge_values({ bx * RASTERIZER_BLOCK_SIZE + RASTERIZER_BLOCK_SIZE, by * RASTERIZER_BLOCK_SIZE + RASTERIZER_BLOCK_SIZE });
// clang-format on
// If the whole block is outside any of the triangle edges we can discard it completely
// We test this by and'ing the relevant edge function values together for all block corners
// and checking if the negative sign bit is set for all of them
if ((b0.x() & b1.x() & b2.x() & b3.x()) & 0x80000000)
continue;
if ((b0.y() & b1.y() & b2.y() & b3.y()) & 0x80000000)
continue;
if ((b0.z() & b1.z() & b2.z() & b3.z()) & 0x80000000)
continue;
// edge value derivatives
auto dbdx = (b1 - b0) / RASTERIZER_BLOCK_SIZE;
auto dbdy = (b2 - b0) / RASTERIZER_BLOCK_SIZE;
// step edge value after each horizontal span: 1 down, BLOCK_SIZE left
auto step_y = dbdy - dbdx * RASTERIZER_BLOCK_SIZE;
int x0 = bx * RASTERIZER_BLOCK_SIZE;
int y0 = by * RASTERIZER_BLOCK_SIZE;
// Generate the coverage mask
if (!options.scissor_enabled && test_point(b0) && test_point(b1) && test_point(b2) && test_point(b3)) {
// The block is fully contained within the triangle. Fill the mask with all 1s
for (int y = 0; y < RASTERIZER_BLOCK_SIZE; y++)
pixel_mask[y] = -1;
} else {
// The block overlaps at least one triangle edge.
// We need to test coverage of every pixel within the block.
auto coords = b0;
for (int y = 0; y < RASTERIZER_BLOCK_SIZE; y++, coords += step_y) {
pixel_mask[y] = 0;
for (int x = 0; x < RASTERIZER_BLOCK_SIZE; x++, coords += dbdx) {
if (test_point(coords) && (!options.scissor_enabled || render_bounds.contains(x0 + x, y0 + y)))
pixel_mask[y] |= 1 << x;
}
}
}
// AND the depth mask onto the coverage mask
if (options.enable_depth_test) {
int z_pass_count = 0;
auto coords = b0;
for (int y = 0; y < RASTERIZER_BLOCK_SIZE; y++, coords += step_y) {
if (pixel_mask[y] == 0) {
coords += dbdx * RASTERIZER_BLOCK_SIZE;
continue;
}
auto* depth = &depth_buffer.scanline(y0 + y)[x0];
for (int x = 0; x < RASTERIZER_BLOCK_SIZE; x++, coords += dbdx, depth++) {
if (~pixel_mask[y] & (1 << x))
continue;
auto barycentric = FloatVector3(coords.x(), coords.y(), coords.z()) * one_over_area;
float z = interpolate(triangle.vertices[0].position.z(), triangle.vertices[1].position.z(), triangle.vertices[2].position.z(), barycentric);
z = options.depth_min + (options.depth_max - options.depth_min) * (z + 1) / 2;
// FIXME: Also apply depth_offset_factor which depends on the depth gradient
z += options.depth_offset_constant * NumericLimits<float>::epsilon();
bool pass = false;
switch (options.depth_func) {
case DepthTestFunction::Always:
pass = true;
break;
case DepthTestFunction::Never:
pass = false;
break;
case DepthTestFunction::Greater:
pass = z > *depth;
break;
case DepthTestFunction::GreaterOrEqual:
pass = z >= *depth;
break;
case DepthTestFunction::NotEqual:
#ifdef __SSE__
pass = z != *depth;
#else
pass = bit_cast<u32>(z) != bit_cast<u32>(*depth);
#endif
break;
case DepthTestFunction::Equal:
#ifdef __SSE__
pass = z == *depth;
#else
//
// This is an interesting quirk that occurs due to us using the x87 FPU when Serenity is
// compiled for the i386 target. When we calculate our depth value to be stored in the buffer,
// it is an 80-bit x87 floating point number, however, when stored into the DepthBuffer, this is
// truncated to 32 bits. This 38 bit loss of precision means that when x87 `FCOMP` is eventually
// used here the comparison fails.
// This could be solved by using a `long double` for the depth buffer, however this would take
// up significantly more space and is completely overkill for a depth buffer. As such, comparing
// the first 32-bits of this depth value is "good enough" that if we get a hit on it being
// equal, we can pretty much guarantee that it's actually equal.
//
pass = bit_cast<u32>(z) == bit_cast<u32>(*depth);
#endif
break;
case DepthTestFunction::LessOrEqual:
pass = z <= *depth;
break;
case DepthTestFunction::Less:
pass = z < *depth;
break;
}
if (!pass) {
pixel_mask[y] ^= 1 << x;
continue;
}
depth_staging[y][x] = z;
z_pass_count++;
}
}
// Nice, no pixels passed the depth test -> block rejected by early z
if (z_pass_count == 0)
continue;
}
// Draw the pixels according to the previously generated mask
auto coords = b0;
for (int y = 0; y < RASTERIZER_BLOCK_SIZE; y++, coords += step_y) {
if (pixel_mask[y] == 0) {
coords += dbdx * RASTERIZER_BLOCK_SIZE;
continue;
}
auto* pixel = pixel_staging[y];
for (int x = 0; x < RASTERIZER_BLOCK_SIZE; x++, coords += dbdx, pixel++) {
if (~pixel_mask[y] & (1 << x))
continue;
// Perspective correct barycentric coordinates
auto barycentric = FloatVector3(coords.x(), coords.y(), coords.z()) * one_over_area;
float interpolated_reciprocal_w = interpolate(triangle.vertices[0].position.w(), triangle.vertices[1].position.w(), triangle.vertices[2].position.w(), barycentric);
float interpolated_w = 1 / interpolated_reciprocal_w;
barycentric = barycentric * FloatVector3(triangle.vertices[0].position.w(), triangle.vertices[1].position.w(), triangle.vertices[2].position.w()) * interpolated_w;
// FIXME: make this more generic. We want to interpolate more than just color and uv
FloatVector4 vertex_color;
if (options.shade_smooth) {
vertex_color = interpolate(
triangle.vertices[0].color,
triangle.vertices[1].color,
triangle.vertices[2].color,
barycentric);
} else {
vertex_color = triangle.vertices[0].color;
}
auto uv = interpolate(
triangle.vertices[0].tex_coord,
triangle.vertices[1].tex_coord,
triangle.vertices[2].tex_coord,
barycentric);
// Calculate depth of fragment for fog
float z = interpolate(triangle.vertices[0].position.z(), triangle.vertices[1].position.z(), triangle.vertices[2].position.z(), barycentric);
z = options.depth_min + (options.depth_max - options.depth_min) * (z + 1) / 2;
*pixel = pixel_shader(uv, vertex_color, z);
}
}
if (options.enable_alpha_test && options.alpha_test_func != AlphaTestFunction::Always) {
for (int y = 0; y < RASTERIZER_BLOCK_SIZE; y++) {
if (pixel_mask[y] == 0)
continue;
auto src = pixel_staging[y];
for (int x = 0; x < RASTERIZER_BLOCK_SIZE; x++, src++) {
if (~pixel_mask[y] & (1 << x))
continue;
bool passed = true;
switch (options.alpha_test_func) {
case AlphaTestFunction::Less:
passed = src->w() < options.alpha_test_ref_value;
break;
case AlphaTestFunction::Equal:
passed = src->w() == options.alpha_test_ref_value;
break;
case AlphaTestFunction::LessOrEqual:
passed = src->w() <= options.alpha_test_ref_value;
break;
case AlphaTestFunction::Greater:
passed = src->w() > options.alpha_test_ref_value;
break;
case AlphaTestFunction::NotEqual:
passed = src->w() != options.alpha_test_ref_value;
break;
case AlphaTestFunction::GreaterOrEqual:
passed = src->w() >= options.alpha_test_ref_value;
break;
case AlphaTestFunction::Never:
case AlphaTestFunction::Always:
VERIFY_NOT_REACHED();
}
if (!passed)
pixel_mask[y] ^= (1 << x);
}
}
}
// Write to depth buffer
if (options.enable_depth_test && options.enable_depth_write) {
for (int y = 0; y < RASTERIZER_BLOCK_SIZE; y++) {
if (pixel_mask[y] == 0)
continue;
auto* depth = &depth_buffer.scanline(y0 + y)[x0];
for (int x = 0; x < RASTERIZER_BLOCK_SIZE; x++, depth++) {
if (~pixel_mask[y] & (1 << x))
continue;
*depth = depth_staging[y][x];
}
}
}
// We will not update the color buffer at all
if (!options.color_mask || !options.enable_color_write)
continue;
if (options.enable_blending) {
// Blend color values from pixel_staging into render_target
for (int y = 0; y < RASTERIZER_BLOCK_SIZE; y++) {
auto src = pixel_staging[y];
auto dst = &render_target.scanline(y0 + y)[x0];
for (int x = 0; x < RASTERIZER_BLOCK_SIZE; x++, src++, dst++) {
if (~pixel_mask[y] & (1 << x))
continue;
auto float_dst = to_vec4(*dst);
auto src_factor = src_constant
+ *src * src_factor_src_color
+ FloatVector4(src->w(), src->w(), src->w(), src->w()) * src_factor_src_alpha
+ float_dst * src_factor_dst_color
+ FloatVector4(float_dst.w(), float_dst.w(), float_dst.w(), float_dst.w()) * src_factor_dst_alpha;
auto dst_factor = dst_constant
+ *src * dst_factor_src_color
+ FloatVector4(src->w(), src->w(), src->w(), src->w()) * dst_factor_src_alpha
+ float_dst * dst_factor_dst_color
+ FloatVector4(float_dst.w(), float_dst.w(), float_dst.w(), float_dst.w()) * dst_factor_dst_alpha;
*dst = (*dst & ~options.color_mask) | (to_rgba32(*src * src_factor + float_dst * dst_factor) & options.color_mask);
}
}
} else {
// Copy color values from pixel_staging into render_target
for (int y = 0; y < RASTERIZER_BLOCK_SIZE; y++) {
auto src = pixel_staging[y];
auto dst = &render_target.scanline(y + y0)[x0];
for (int x = 0; x < RASTERIZER_BLOCK_SIZE; x++, src++, dst++) {
if (~pixel_mask[y] & (1 << x))
continue;
*dst = (*dst & ~options.color_mask) | (to_rgba32(*src) & options.color_mask);
}
}
}
}
}
}
static Gfx::IntSize closest_multiple(const Gfx::IntSize& min_size, size_t step)
{
int width = ((min_size.width() + step - 1) / step) * step;
int height = ((min_size.height() + step - 1) / step) * step;
return { width, height };
}
Device::Device(const Gfx::IntSize& min_size)
: m_render_target { Gfx::Bitmap::try_create(Gfx::BitmapFormat::BGRA8888, closest_multiple(min_size, RASTERIZER_BLOCK_SIZE)).release_value_but_fixme_should_propagate_errors() }
, m_depth_buffer { adopt_own(*new DepthBuffer(closest_multiple(min_size, RASTERIZER_BLOCK_SIZE))) }
{
m_options.scissor_box = m_render_target->rect();
}
DeviceInfo Device::info() const
{
return {
.vendor_name = "SerenityOS",
.device_name = "SoftGPU",
.num_texture_units = num_samplers
};
}
void Device::draw_primitives(PrimitiveType primitive_type, FloatMatrix4x4 const& transform, FloatMatrix4x4 const& texture_matrix, Vector<Vertex> const& vertices, Vector<size_t> const& enabled_texture_units)
{
// At this point, the user has effectively specified that they are done with defining the geometry
// of what they want to draw. We now need to do a few things (https://www.khronos.org/opengl/wiki/Rendering_Pipeline_Overview):
//
// 1. Transform all of the vertices in the current vertex list into eye space by mulitplying the model-view matrix
// 2. Transform all of the vertices from eye space into clip space by multiplying by the projection matrix
// 3. If culling is enabled, we cull the desired faces (https://learnopengl.com/Advanced-OpenGL/Face-culling)
// 4. Each element of the vertex is then divided by w to bring the positions into NDC (Normalized Device Coordinates)
// 5. The vertices are sorted (for the rasteriser, how are we doing this? 3Dfx did this top to bottom in terms of vertex y coordinates)
// 6. The vertices are then sent off to the rasteriser and drawn to the screen
float scr_width = m_render_target->width();
float scr_height = m_render_target->height();
m_triangle_list.clear_with_capacity();
m_processed_triangles.clear_with_capacity();
// Let's construct some triangles
if (primitive_type == PrimitiveType::Triangles) {
Triangle triangle;
for (size_t i = 0; i < vertices.size(); i += 3) {
triangle.vertices[0] = vertices.at(i);
triangle.vertices[1] = vertices.at(i + 1);
triangle.vertices[2] = vertices.at(i + 2);
m_triangle_list.append(triangle);
}
} else if (primitive_type == PrimitiveType::Quads) {
// We need to construct two triangles to form the quad
Triangle triangle;
VERIFY(vertices.size() % 4 == 0);
for (size_t i = 0; i < vertices.size(); i += 4) {
// Triangle 1
triangle.vertices[0] = vertices.at(i);
triangle.vertices[1] = vertices.at(i + 1);
triangle.vertices[2] = vertices.at(i + 2);
m_triangle_list.append(triangle);
// Triangle 2
triangle.vertices[0] = vertices.at(i + 2);
triangle.vertices[1] = vertices.at(i + 3);
triangle.vertices[2] = vertices.at(i);
m_triangle_list.append(triangle);
}
} else if (primitive_type == PrimitiveType::TriangleFan) {
Triangle triangle;
triangle.vertices[0] = vertices.at(0); // Root vertex is always the vertex defined first
for (size_t i = 1; i < vertices.size() - 1; i++) // This is technically `n-2` triangles. We start at index 1
{
triangle.vertices[1] = vertices.at(i);
triangle.vertices[2] = vertices.at(i + 1);
m_triangle_list.append(triangle);
}
} else if (primitive_type == PrimitiveType::TriangleStrip) {
Triangle triangle;
for (size_t i = 0; i < vertices.size() - 2; i++) {
if (i % 2 == 0) {
triangle.vertices[0] = vertices.at(i);
triangle.vertices[1] = vertices.at(i + 1);
triangle.vertices[2] = vertices.at(i + 2);
} else {
triangle.vertices[0] = vertices.at(i + 1);
triangle.vertices[1] = vertices.at(i);
triangle.vertices[2] = vertices.at(i + 2);
}
m_triangle_list.append(triangle);
}
}
// Now let's transform each triangle and send that to the GPU
for (size_t i = 0; i < m_triangle_list.size(); i++) {
Triangle& triangle = m_triangle_list.at(i);
// First multiply the vertex by the MODELVIEW matrix and then the PROJECTION matrix
triangle.vertices[0].position = transform * triangle.vertices[0].position;
triangle.vertices[1].position = transform * triangle.vertices[1].position;
triangle.vertices[2].position = transform * triangle.vertices[2].position;
// Apply texture transformation
// FIXME: implement multi-texturing: texcoords should be stored per texture unit
triangle.vertices[0].tex_coord = texture_matrix * triangle.vertices[0].tex_coord;
triangle.vertices[1].tex_coord = texture_matrix * triangle.vertices[1].tex_coord;
triangle.vertices[2].tex_coord = texture_matrix * triangle.vertices[2].tex_coord;
// At this point, we're in clip space
// Here's where we do the clipping. This is a really crude implementation of the
// https://learnopengl.com/Getting-started/Coordinate-Systems
// "Note that if only a part of a primitive e.g. a triangle is outside the clipping volume OpenGL
// will reconstruct the triangle as one or more triangles to fit inside the clipping range. "
//
// ALL VERTICES ARE DEFINED IN A CLOCKWISE ORDER
// Okay, let's do some face culling first
m_clipped_vertices.clear_with_capacity();
m_clipped_vertices.append(triangle.vertices[0]);
m_clipped_vertices.append(triangle.vertices[1]);
m_clipped_vertices.append(triangle.vertices[2]);
m_clipper.clip_triangle_against_frustum(m_clipped_vertices);
if (m_clipped_vertices.size() < 3)
continue;
for (auto& vec : m_clipped_vertices) {
// perspective divide
float w = vec.position.w();
vec.position.set_x(vec.position.x() / w);
vec.position.set_y(vec.position.y() / w);
vec.position.set_z(vec.position.z() / w);
vec.position.set_w(1 / w);
// to screen space
vec.position.set_x(scr_width / 2 + vec.position.x() * scr_width / 2);
vec.position.set_y(scr_height / 2 - vec.position.y() * scr_height / 2);
}
Triangle tri;
tri.vertices[0] = m_clipped_vertices[0];
for (size_t i = 1; i < m_clipped_vertices.size() - 1; i++) {
tri.vertices[1] = m_clipped_vertices[i];
tri.vertices[2] = m_clipped_vertices[i + 1];
m_processed_triangles.append(tri);
}
}
for (size_t i = 0; i < m_processed_triangles.size(); i++) {
Triangle& triangle = m_processed_triangles.at(i);
// Let's calculate the (signed) area of the triangle
// https://cp-algorithms.com/geometry/oriented-triangle-area.html
float dxAB = triangle.vertices[0].position.x() - triangle.vertices[1].position.x(); // A.x - B.x
float dxBC = triangle.vertices[1].position.x() - triangle.vertices[2].position.x(); // B.X - C.x
float dyAB = triangle.vertices[0].position.y() - triangle.vertices[1].position.y();
float dyBC = triangle.vertices[1].position.y() - triangle.vertices[2].position.y();
float area = (dxAB * dyBC) - (dxBC * dyAB);
if (area == 0.0f)
continue;
if (m_options.enable_culling) {
bool is_front = (m_options.front_face == WindingOrder::CounterClockwise ? area < 0 : area > 0);
if (!is_front && m_options.cull_back)
continue;
if (is_front && m_options.cull_front)
continue;
}
if (area > 0) {
swap(triangle.vertices[0], triangle.vertices[1]);
}
submit_triangle(triangle, enabled_texture_units);
}
}
void Device::submit_triangle(const Triangle& triangle, Vector<size_t> const& enabled_texture_units)
{
rasterize_triangle(m_options, *m_render_target, *m_depth_buffer, triangle, [this, &enabled_texture_units](FloatVector4 const& uv, FloatVector4 const& color, float z) -> FloatVector4 {
FloatVector4 fragment = color;
for (size_t i : enabled_texture_units) {
// FIXME: implement GL_TEXTURE_1D, GL_TEXTURE_3D and GL_TEXTURE_CUBE_MAP
auto const& sampler = m_samplers[i];
FloatVector4 texel = sampler.sample_2d({ uv.x(), uv.y() });
// FIXME: Implement more blend modes
switch (sampler.config().fixed_function_texture_env_mode) {
case TextureEnvMode::Modulate:
default:
fragment = fragment * texel;
break;
case TextureEnvMode::Replace:
fragment = texel;
break;
case TextureEnvMode::Decal: {
float src_alpha = fragment.w();
float one_minus_src_alpha = 1 - src_alpha;
fragment.set_x(texel.x() * src_alpha + fragment.x() * one_minus_src_alpha);
fragment.set_y(texel.y() * src_alpha + fragment.y() * one_minus_src_alpha);
fragment.set_z(texel.z() * src_alpha + fragment.z() * one_minus_src_alpha);
break;
}
}
}
// Calculate fog
// Math from here: https://opengl-notes.readthedocs.io/en/latest/topics/texturing/aliasing.html
if (m_options.fog_enabled) {
float factor = 0.0f;
switch (m_options.fog_mode) {
case FogMode::Linear:
factor = (m_options.fog_end - z) / (m_options.fog_end - m_options.fog_start);
break;
case FogMode::Exp:
factor = exp(-((m_options.fog_density * z)));
break;
case FogMode::Exp2:
factor = exp(-((m_options.fog_density * z) * (m_options.fog_density * z)));
break;
default:
break;
}
// Mix texel with fog
fragment = mix(m_options.fog_color, fragment, factor);
}
return fragment;
});
}
void Device::resize(const Gfx::IntSize& min_size)
{
wait_for_all_threads();
m_render_target = Gfx::Bitmap::try_create(Gfx::BitmapFormat::BGRA8888, closest_multiple(min_size, RASTERIZER_BLOCK_SIZE)).release_value_but_fixme_should_propagate_errors();
m_depth_buffer = adopt_own(*new DepthBuffer(m_render_target->size()));
}
void Device::clear_color(const FloatVector4& color)
{
wait_for_all_threads();
uint8_t r = static_cast<uint8_t>(clamp(color.x(), 0.0f, 1.0f) * 255);
uint8_t g = static_cast<uint8_t>(clamp(color.y(), 0.0f, 1.0f) * 255);
uint8_t b = static_cast<uint8_t>(clamp(color.z(), 0.0f, 1.0f) * 255);
uint8_t a = static_cast<uint8_t>(clamp(color.w(), 0.0f, 1.0f) * 255);
auto const fill_color = Gfx::Color(r, g, b, a);
if (m_options.scissor_enabled) {
auto fill_rect = m_render_target->rect();
fill_rect.intersect(scissor_box_to_window_coordinates(m_options.scissor_box, fill_rect));
Gfx::Painter painter { *m_render_target };
painter.fill_rect(fill_rect, fill_color);
return;
}
m_render_target->fill(fill_color);
}
void Device::clear_depth(float depth)
{
wait_for_all_threads();
if (m_options.scissor_enabled) {
m_depth_buffer->clear(scissor_box_to_window_coordinates(m_options.scissor_box, m_render_target->rect()), depth);
return;
}
m_depth_buffer->clear(depth);
}
void Device::blit(Gfx::Bitmap const& source, int x, int y)
{
wait_for_all_threads();
Gfx::Painter painter { *m_render_target };
painter.blit({ x, y }, source, source.rect(), 1.0f, true);
}
void Device::blit_to(Gfx::Bitmap& target)
{
wait_for_all_threads();
Gfx::Painter painter { target };
painter.blit({ 0, 0 }, *m_render_target, m_render_target->rect(), 1.0f, false);
}
void Device::wait_for_all_threads() const
{
// FIXME: Wait for all render threads to finish when multithreading is being implemented
}
void Device::set_options(const RasterizerOptions& options)
{
wait_for_all_threads();
m_options = options;
// FIXME: Recreate or reinitialize render threads here when multithreading is being implemented
}
Gfx::RGBA32 Device::get_backbuffer_pixel(int x, int y)
{
// FIXME: Reading individual pixels is very slow, rewrite this to transfer whole blocks
if (x < 0 || y < 0 || x >= m_render_target->width() || y >= m_render_target->height())
return 0;
return m_render_target->scanline(y)[x];
}
float Device::get_depthbuffer_value(int x, int y)
{
// FIXME: Reading individual pixels is very slow, rewrite this to transfer whole blocks
if (x < 0 || y < 0 || x >= m_render_target->width() || y >= m_render_target->height())
return 1.0f;
return m_depth_buffer->scanline(y)[x];
}
NonnullRefPtr<Image> Device::create_image(ImageFormat format, unsigned width, unsigned height, unsigned depth, unsigned levels, unsigned layers)
{
VERIFY(width > 0);
VERIFY(height > 0);
VERIFY(depth > 0);
VERIFY(levels > 0);
VERIFY(layers > 0);
return adopt_ref(*new Image(format, width, height, depth, levels, layers));
}
void Device::set_sampler_config(unsigned sampler, SamplerConfig const& config)
{
m_samplers[sampler].set_config(config);
}
}
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