Implement submerging in SDL_gpu builds.

data/shaders/default.frag

@@ -8,6 +8,13 @@ uniform sampler2D tex;
 
 void main()
 {
+
+	float submerge_alpha = 0;
+	if (frag_texture_pos.y > 1.0 - frag_submerge) {
+		submerge_alpha = 0.7 + (frag_texture_pos.y - (1 - frag_submerge))
+				/ frag_submerge * 0.3;
+	}
+	vec4 submerge_mod = vec4(0, 0, 0, submerge_alpha);
 	gl_FragColor = texture2D(tex, frag_texture_pos)
-					+ frag_draw_color + frag_color_mod;
+					+ frag_draw_color + frag_color_mod - submerge_mod;
 }

src/display.cpp

@@ -1696,34 +1696,9 @@ void display::render_image(int x, int y, const display::tdrawing_layer drawing_l
 	}
 #ifdef SDL_GPU
 	sdl::timage img(surf);
+	img.set_submerge(submerged);
 
-	if(submerged > 0.0) {
-		// divide the surface into 2 parts
-		const int submerge_height = std::max<int>(0, surf->h*(1.0-submerged));
-		//const int depth = surf->h - submerge_height;
-		SDL_Rect srcrect = sdl::create_rect(0, 0, surf->w, submerge_height);
-		img.set_clip(srcrect);
-		drawing_buffer_add(drawing_layer, loc, x, y, img);
-
-		if(submerge_height != surf->h) {
-			//the lower part will be transparent
-			//float alpha_base = 0.3f; // 30% alpha at surface of water
-			float alpha_delta = 0.015f; // lose 1.5% per pixel depth
-			alpha_delta *= zoom_ / DefaultZoom; // adjust with zoom
-			//TODO: submerging
-			//surf = submerge_alpha(surf, depth, alpha_base, alpha_delta, false);
-
-			srcrect.y = submerge_height;
-			srcrect.h = surf->h-submerge_height;
-			y += submerge_height;
-
-			img.set_clip(srcrect);
-			drawing_buffer_add(drawing_layer, loc, x, y, img);
-		}
-	} else {
-		// simple blit
-		drawing_buffer_add(drawing_layer, loc, x, y, img);
-	}
+	drawing_buffer_add(drawing_layer, loc, x, y, img);
 #else
 	if(submerged > 0.0) {
 		// divide the surface into 2 parts

src/sdl/image.cpp

@@ -87,9 +87,12 @@ timage::timage(const surface &source)
 	, hwrap_(GPU_WRAP_NONE)
 	, vwrap_(GPU_WRAP_NONE)
 	, smooth_(false)
+	, submerge_(0)
 {
 	if (image_ == NULL) {
-		throw tgpu_exception("Failed to construct timage object.", true);
+		if (!source.null()) {
+			throw tgpu_exception("Failed to construct timage object.", true);
+		}
 	} else {
 		clip_ = create_gpu_rect(0, 0, image_->w, image_->h);
 		image_->refcount = 1;
@@ -111,9 +114,12 @@ timage::timage(SDL_Surface *source)
 	, hwrap_(GPU_WRAP_NONE)
 	, vwrap_(GPU_WRAP_NONE)
 	, smooth_(false)
+	, submerge_(0)
 {
 	if (image_ == NULL) {
-		throw tgpu_exception("Failed to construct timage object.", true);
+		if (source != NULL) {
+			throw tgpu_exception("Failed to construct timage object.", true);
+		}
 	} else {
 		clip_ = create_gpu_rect(0, 0, image_->w, image_->h);
 		image_->refcount = 1;
@@ -135,6 +141,7 @@ timage::timage()
 	, hwrap_(GPU_WRAP_NONE)
 	, vwrap_(GPU_WRAP_NONE)
 	, smooth_(false)
+	, submerge_(0)
 {
 }
 
@@ -161,6 +168,7 @@ timage::timage(const timage &texture)
 	, hwrap_(texture.hwrap_)
 	, vwrap_(texture.vwrap_)
 	, smooth_(texture.smooth_)
+	, submerge_(texture.submerge_)
 {
 	if (image_ != NULL) {
 		image_->refcount += 1;
@@ -182,6 +190,7 @@ void timage::draw(CVideo &video, const int x, const int y)
 	GPU_SetImageFilter(image_, smooth_ ? GPU_FILTER_LINEAR : GPU_FILTER_NEAREST);
 	GPU_SetWrapMode(image_, hwrap_, vwrap_);
 	video.set_texture_color_modulation(red_mod_, green_mod_, blue_mod_, alpha_mod_);
+	video.set_texture_submerge(float(submerge_));
 	GPU_BlitTransform(image_, &clip_, video.render_target(), x + width()/2, y + height()/2,
 					  rotation_, hscale_, vscale_);
 }
@@ -329,6 +338,16 @@ GPU_WrapEnum timage::vwrap() const
 	return vwrap_;
 }
 
+void timage::set_submerge(double val)
+{
+	submerge_ = val;
+}
+
+double timage::submerge() const
+{
+	return submerge_;
+}
+
 bool timage::null() const
 {
 	return image_ == NULL;
@@ -345,6 +364,7 @@ timage timage::clone() const
 	res.set_rotation(rotation());
 	res.set_scale(hscale(), vscale());
 	res.set_smooth_scaling(smooth_scaling());
+	res.set_submerge(submerge_);
 
 	return res;
 }

src/sdl/image.hpp

@@ -239,6 +239,10 @@ public:
 	 */
 	GPU_WrapEnum vwrap( )const;
 
+	void set_submerge(double val);
+
+	double submerge() const;
+
 	/**
 	 * Returns true if the managed texture is NULL.
 	 */
@@ -270,6 +274,9 @@ private:
 
 	/** Smooth scaling. */
 	bool smooth_;
+
+	/** Submerge. */
+	double submerge_;
 };
 }
 #endif

src/sdl/shader.cpp

@@ -44,6 +44,8 @@ shader_program::shader_program(const std::string &vsrc, const std::string &fsrc)
 
 	attr_color_mod_ = GPU_GetAttributeLocation(program_object_,
 											   "vert_color_mod");
+	attr_submerge_ = GPU_GetAttributeLocation(program_object_,
+											  "vert_submerge");
 	set_color_mod(0, 0, 0, 0);
 	set_submerge(0);
 }