gfx_api: Use a single (huge) triangle that covers the screen to rende…

…r offscreen framebuffer

data/base/shaders/vk/world_to_screen.vert

@@ -5,14 +5,13 @@ layout(std140, set = 0, binding = 0) uniform cbuffer {
 };
 
 layout(location = 0) in vec2 vertexPos;
-layout(location = 1) in vec2 vertexTexCoords;
 
 layout(location = 0) out vec2 texCoords;
 
 void main()
 {
-	texCoords = vertexTexCoords;
-	gl_Position = vec4(vertexPos.x, vertexPos.y, 0.f, 1.f);
+	gl_Position = vec4(vertexPos.x, vertexPos.y, 0.0, 1.0);
+	texCoords = 0.5 * gl_Position.xy + vec2(0.5);
 //	gl_Position.y *= -1.;
 //	gl_Position.z = (gl_Position.z + gl_Position.w) / 2.0;
 }

data/base/shaders/world_to_screen.vert

@@ -3,10 +3,8 @@
 
 #if (!defined(GL_ES) && (__VERSION__ >= 130)) || (defined(GL_ES) && (__VERSION__ >= 300))
 in vec2 vertexPos;
-in vec2 vertexTexCoords;
 #else
 attribute vec2 vertexPos;
-attribute vec2 vertexTexCoords;
 #endif
 
 #if (!defined(GL_ES) && (__VERSION__ >= 130)) || (defined(GL_ES) && (__VERSION__ >= 300))
@@ -17,6 +15,6 @@ varying vec2 texCoords;
 
 void main()
 {
-	texCoords = vertexTexCoords;
-	gl_Position = vec4(vertexPos.x, vertexPos.y, 0.f, 1.f);
+	gl_Position = vec4(vertexPos.x, vertexPos.y, 0.0, 1.0);
+	texCoords = 0.5 * gl_Position.xy + vec2(0.5);
 }

lib/ivis_opengl/gfx_api.h

@@ -1250,9 +1250,8 @@ namespace gfx_api
 	using WorldToScreenPSO = typename gfx_api::pipeline_state_helper<rasterizer_state<REND_OPAQUE, DEPTH_CMP_ALWAYS_WRT_OFF, 255, polygon_offset::disabled, stencil_mode::stencil_disabled, cull_mode::none>, primitive_type::triangles, index_type::u16,
 	std::tuple<constant_buffer_type<SHADER_WORLD_TO_SCREEN>>,
 	std::tuple<
-		vertex_buffer_description<4 * sizeof(gfxFloat), gfx_api::vertex_attribute_input_rate::vertex,
-			vertex_attribute_description<position, gfx_api::vertex_attribute_type::float2, 0>,
-			vertex_attribute_description<texcoord, gfx_api::vertex_attribute_type::float2, sizeof(gfxFloat)*2>
+		vertex_buffer_description<2 * sizeof(gfxFloat), gfx_api::vertex_attribute_input_rate::vertex,
+			vertex_attribute_description<position, gfx_api::vertex_attribute_type::float2, 0>
 		>
 	>,
 	std::tuple<texture_description<0, sampler_type::bilinear, pixel_format_target::texture_2d>>, SHADER_WORLD_TO_SCREEN>;

src/display3d.cpp

@@ -144,7 +144,7 @@ static WzText txtShowOrders;
 // show Droid visible/draw counts text
 static WzText droidText;
 
-static gfx_api::buffer* pScreenQuadVBO = nullptr;
+static gfx_api::buffer* pScreenTriangleVBO = nullptr;
 
 
 /********************  Variables  ********************/
@@ -1455,10 +1455,10 @@ static void drawTiles(iView *player)
 	// Draw the scene to the default framebuffer
 	gfx_api::WorldToScreenPSO::get().bind();
 	gfx_api::WorldToScreenPSO::get().bind_constants({1.0f});
-	gfx_api::WorldToScreenPSO::get().bind_vertex_buffers(pScreenQuadVBO);
+	gfx_api::WorldToScreenPSO::get().bind_vertex_buffers(pScreenTriangleVBO);
 	gfx_api::WorldToScreenPSO::get().bind_textures(gfx_api::context::get().getSceneTexture());
 	gfx_api::WorldToScreenPSO::get().draw(6, 0);
-	gfx_api::WorldToScreenPSO::get().unbind_vertex_buffers(pScreenQuadVBO);
+	gfx_api::WorldToScreenPSO::get().unbind_vertex_buffers(pScreenTriangleVBO);
 }
 
 /// Initialise the fog, skybox and some other stuff
@@ -1507,19 +1507,14 @@ bool init3DView()
 	batchedObjectStatusRenderer.initialize();
 
 
-	// vertex attributes for screen-filling quad in NDC
-	gfx_api::gfxFloat screenQuadVertices[] = {
-		// position   // texCoord
-		-1.0f,  1.0f,  0.0f, 1.0f,
-		-1.0f, -1.0f,  0.0f, 0.0f,
-		 1.0f, -1.0f,  1.0f, 0.0f,
-		//
-		-1.0f,  1.0f,  0.0f, 1.0f,
-		 1.0f, -1.0f,  1.0f, 0.0f,
-		 1.0f,  1.0f,  1.0f, 1.0f
+	// vertex attributes for a single triangle that covers the screen
+	gfx_api::gfxFloat screenTriangleVertices[] = {
+		-1.f, -1.f,
+		3.f, -1.f,
+		-1.f, 3.f
 	};
-	pScreenQuadVBO = gfx_api::context::get().create_buffer_object(gfx_api::buffer::usage::vertex_buffer, gfx_api::context::buffer_storage_hint::static_draw, "screenQuadVertices");
-	pScreenQuadVBO->upload(sizeof(screenQuadVertices), screenQuadVertices);
+	pScreenTriangleVBO = gfx_api::context::get().create_buffer_object(gfx_api::buffer::usage::vertex_buffer, gfx_api::context::buffer_storage_hint::static_draw, "screenTriangleVertices");
+	pScreenTriangleVBO->upload(sizeof(screenTriangleVertices), screenTriangleVertices);
 
 	return true;
 }
@@ -1550,8 +1545,8 @@ void shutdown3DView_FullReset()
 	// in this function, which is called from stageTwoShutdown (as opposed to stageThreeShutdown, which is called from levReleaseMissionData)...
 	batchedObjectStatusRenderer.reset();
 
-	delete pScreenQuadVBO;
-	pScreenQuadVBO = nullptr;
+	delete pScreenTriangleVBO;
+	pScreenTriangleVBO = nullptr;
 }
 
 /// set the view position from save game