Add resolution scaling to Vulkan renderer

This commit adds a new cvar called vk_pixel_size that represents how big
pixels should look in the rendered world in order to simulate lower
screen resolutions. With its default value of 1 everything looks normal,
but with bigger sizes (e.g. 4) the rendered world starts to look
"pixelated" due to pixels appearing bigger.

To implement the effect, the viewport and scissor are modified when
drawing the world so the rendering results cover a smaller area in the
top-left corner of the image.

The post-processing fragment shader is used to scale the image back to
the swapchain size before drawing UI elements on top of it.

The UI is not affected by this change, so the existing UI scaling
options continue to work as before with no changes, adding some
flexibility to the mix.

Related to feature request #588.

doc/040_cvarlist.md

@@ -405,6 +405,12 @@ it's `+set busywait 0` (setting the `busywait` cvar) and `-portable`
 
 * **vk_picmip**: Shrink factor for the textures. (default: `0`)
 
+* **vk_pixel_size**: Pixel size when rendering the world, used to simulate
+  lower screen resolutions. The value represents the length, in pixels, of the
+  side of each pixel block. For example, with size 2 pixels are 2x2 squares,
+  and at 1600x1200 the image is effectively an upscaled 800x600 image.
+  (default: `1`)
+
 * **vk_dynamic**: Use dynamic lighting. (default: `1`)
 
 * **vk_showtris**: Display mesh triangles. (default: `0`)

src/client/refresh/vk/header/local.h

@@ -145,6 +145,7 @@ extern	cvar_t	*vk_flashblend;
 extern	cvar_t	*vk_finish;
 extern	cvar_t	*vk_polyblend;
 extern	cvar_t	*vk_shadows;
+extern	cvar_t	*vk_pixel_size;
 extern	cvar_t	*vk_particle_size;
 extern	cvar_t	*vk_particle_att_a;
 extern	cvar_t	*vk_particle_att_b;
@@ -294,6 +295,7 @@ typedef struct
 	qboolean stereo_enabled;
 
 	VkPipeline current_pipeline;
+	qvkrenderpasstype_t current_renderpass;
 } vkstate_t;
 
 extern vkconfig_t  vk_config;

src/client/refresh/vk/spirv/world_warp_frag.c

@@ -1,42 +1,44 @@
-	// 8.13.3559
+	// 1011.0.0
 	 #pragma once
 const uint32_t world_warp_frag_spv[] = {
-	0x07230203,0x00010000,0x00080008,0x00000078,0x00000000,0x00020011,0x00000001,0x0006000b,
+	0x07230203,0x00010000,0x0008000a,0x0000007e,0x00000000,0x00020011,0x00000001,0x0006000b,
 	0x00000001,0x4c534c47,0x6474732e,0x3035342e,0x00000000,0x0003000e,0x00000000,0x00000001,
-	0x0007000f,0x00000004,0x00000004,0x6e69616d,0x00000000,0x0000000c,0x00000070,0x00030010,
+	0x0007000f,0x00000004,0x00000004,0x6e69616d,0x00000000,0x0000000c,0x00000076,0x00030010,
 	0x00000004,0x00000007,0x00030003,0x00000002,0x000001c2,0x00090004,0x415f4c47,0x735f4252,
 	0x72617065,0x5f657461,0x64616873,0x6f5f7265,0x63656a62,0x00007374,0x00040005,0x00000004,
 	0x6e69616d,0x00000000,0x00030005,0x00000009,0x00007675,0x00060005,0x0000000c,0x465f6c67,
 	0x43676172,0x64726f6f,0x00000000,0x00060005,0x00000012,0x68737550,0x736e6f43,0x746e6174,
 	0x00000000,0x00050006,0x00000012,0x00000000,0x656d6974,0x00000000,0x00050006,0x00000012,
 	0x00000001,0x6c616373,0x00000065,0x00060006,0x00000012,0x00000002,0x57726373,0x68746469,
-	0x00000000,0x00060006,0x00000012,0x00000003,0x48726373,0x68676965,0x00000074,0x00030005,
+	0x00000000,0x00060006,0x00000012,0x00000003,0x48726373,0x68676965,0x00000074,0x00060006,
-	0x00000014,0x00006370,0x00030005,0x0000002c,0x00007873,0x00030005,0x0000003d,0x00007973,
+	0x00000012,0x00000004,0x65786970,0x7a69536c,0x00000065,0x00030005,0x00000014,0x00006370,
-	0x00040005,0x0000004c,0x69685378,0x00007466,0x00040005,0x00000057,0x69685379,0x00007466,
+	0x00030005,0x0000002c,0x00007873,0x00030005,0x0000003d,0x00007973,0x00040005,0x0000004c,
-	0x00050005,0x00000060,0x74736964,0x6974726f,0x00006e6f,0x00060005,0x00000070,0x67617266,
+	0x69685378,0x00007466,0x00040005,0x00000057,0x69685379,0x00007466,0x00050005,0x00000060,
-	0x746e656d,0x6f6c6f43,0x00000072,0x00050005,0x00000074,0x78655473,0x65727574,0x00000000,
+	0x74736964,0x6974726f,0x00006e6f,0x00060005,0x00000076,0x67617266,0x746e656d,0x6f6c6f43,
-	0x00040047,0x0000000c,0x0000000b,0x0000000f,0x00050048,0x00000012,0x00000000,0x00000023,
+	0x00000072,0x00050005,0x0000007a,0x78655473,0x65727574,0x00000000,0x00040047,0x0000000c,
-	0x00000044,0x00050048,0x00000012,0x00000001,0x00000023,0x00000048,0x00050048,0x00000012,
+	0x0000000b,0x0000000f,0x00050048,0x00000012,0x00000000,0x00000023,0x00000044,0x00050048,
-	0x00000002,0x00000023,0x0000004c,0x00050048,0x00000012,0x00000003,0x00000023,0x00000050,
+	0x00000012,0x00000001,0x00000023,0x00000048,0x00050048,0x00000012,0x00000002,0x00000023,
-	0x00030047,0x00000012,0x00000002,0x00040047,0x00000070,0x0000001e,0x00000000,0x00040047,
+	0x0000004c,0x00050048,0x00000012,0x00000003,0x00000023,0x00000050,0x00050048,0x00000012,
-	0x00000074,0x00000022,0x00000000,0x00040047,0x00000074,0x00000021,0x00000000,0x00020013,
+	0x00000004,0x00000023,0x00000054,0x00030047,0x00000012,0x00000002,0x00040047,0x00000076,
-	0x00000002,0x00030021,0x00000003,0x00000002,0x00030016,0x00000006,0x00000020,0x00040017,
+	0x0000001e,0x00000000,0x00040047,0x0000007a,0x00000022,0x00000000,0x00040047,0x0000007a,
-	0x00000007,0x00000006,0x00000002,0x00040020,0x00000008,0x00000007,0x00000007,0x00040017,
+	0x00000021,0x00000000,0x00020013,0x00000002,0x00030021,0x00000003,0x00000002,0x00030016,
-	0x0000000a,0x00000006,0x00000004,0x00040020,0x0000000b,0x00000001,0x0000000a,0x0004003b,
+	0x00000006,0x00000020,0x00040017,0x00000007,0x00000006,0x00000002,0x00040020,0x00000008,
-	0x0000000b,0x0000000c,0x00000001,0x00040015,0x0000000d,0x00000020,0x00000000,0x0004002b,
+	0x00000007,0x00000007,0x00040017,0x0000000a,0x00000006,0x00000004,0x00040020,0x0000000b,
-	0x0000000d,0x0000000e,0x00000000,0x00040020,0x0000000f,0x00000001,0x00000006,0x0006001e,
+	0x00000001,0x0000000a,0x0004003b,0x0000000b,0x0000000c,0x00000001,0x00040015,0x0000000d,
-	0x00000012,0x00000006,0x00000006,0x00000006,0x00000006,0x00040020,0x00000013,0x00000009,
+	0x00000020,0x00000000,0x0004002b,0x0000000d,0x0000000e,0x00000000,0x00040020,0x0000000f,
-	0x00000012,0x0004003b,0x00000013,0x00000014,0x00000009,0x00040015,0x00000015,0x00000020,
+	0x00000001,0x00000006,0x0007001e,0x00000012,0x00000006,0x00000006,0x00000006,0x00000006,
-	0x00000001,0x0004002b,0x00000015,0x00000016,0x00000002,0x00040020,0x00000017,0x00000009,
+	0x00000006,0x00040020,0x00000013,0x00000009,0x00000012,0x0004003b,0x00000013,0x00000014,
-	0x00000006,0x0004002b,0x0000000d,0x0000001b,0x00000001,0x0004002b,0x00000015,0x0000001e,
+	0x00000009,0x00040015,0x00000015,0x00000020,0x00000001,0x0004002b,0x00000015,0x00000016,
-	0x00000003,0x0004002b,0x00000015,0x00000023,0x00000000,0x0004002b,0x00000006,0x00000026,
+	0x00000002,0x00040020,0x00000017,0x00000009,0x00000006,0x0004002b,0x0000000d,0x0000001b,
-	0x00000000,0x00020014,0x00000027,0x00040020,0x0000002b,0x00000007,0x00000006,0x0004002b,
+	0x00000001,0x0004002b,0x00000015,0x0000001e,0x00000003,0x0004002b,0x00000015,0x00000023,
-	0x00000015,0x0000002d,0x00000001,0x0004002b,0x00000006,0x00000032,0x40000000,0x0004002b,
+	0x00000000,0x0004002b,0x00000006,0x00000026,0x00000000,0x00020014,0x00000027,0x00040020,
-	0x00000006,0x00000052,0x40490e56,0x0004002b,0x00000006,0x00000054,0x41200000,0x0004002b,
+	0x0000002b,0x00000007,0x00000006,0x0004002b,0x00000015,0x0000002d,0x00000001,0x0004002b,
-	0x00000006,0x0000006a,0x3bda3c21,0x00040020,0x0000006f,0x00000003,0x0000000a,0x0004003b,
+	0x00000006,0x00000032,0x40000000,0x0004002b,0x00000006,0x00000052,0x40490e56,0x0004002b,
-	0x0000006f,0x00000070,0x00000003,0x00090019,0x00000071,0x00000006,0x00000001,0x00000000,
+	0x00000006,0x00000054,0x41200000,0x0004002b,0x00000006,0x0000006a,0x3bda3c21,0x0004002b,
-	0x00000000,0x00000000,0x00000001,0x00000000,0x0003001b,0x00000072,0x00000071,0x00040020,
+	0x00000015,0x0000006f,0x00000004,0x00040020,0x00000075,0x00000003,0x0000000a,0x0004003b,
-	0x00000073,0x00000000,0x00000072,0x0004003b,0x00000073,0x00000074,0x00000000,0x00050036,
+	0x00000075,0x00000076,0x00000003,0x00090019,0x00000077,0x00000006,0x00000001,0x00000000,
+	0x00000000,0x00000000,0x00000001,0x00000000,0x0003001b,0x00000078,0x00000077,0x00040020,
+	0x00000079,0x00000000,0x00000078,0x0004003b,0x00000079,0x0000007a,0x00000000,0x00050036,
 	0x00000002,0x00000004,0x00000000,0x00000003,0x000200f8,0x00000005,0x0004003b,0x00000008,
 	0x00000009,0x00000007,0x0004003b,0x0000002b,0x0000002c,0x00000007,0x0004003b,0x0000002b,
 	0x0000003d,0x00000007,0x0004003b,0x0000002b,0x0000004c,0x00000007,0x0004003b,0x0000002b,
@@ -87,7 +89,10 @@ const uint32_t world_warp_frag_spv[] = {
 	0x0000006a,0x0003003e,0x00000060,0x0000006b,0x0004003d,0x00000007,0x0000006c,0x00000060,
 	0x0004003d,0x00000007,0x0000006d,0x00000009,0x00050081,0x00000007,0x0000006e,0x0000006d,
 	0x0000006c,0x0003003e,0x00000009,0x0000006e,0x000200f9,0x0000002a,0x000200f8,0x0000002a,
-	0x0004003d,0x00000072,0x00000075,0x00000074,0x0004003d,0x00000007,0x00000076,0x00000009,
+	0x00050041,0x00000017,0x00000070,0x00000014,0x0000006f,0x0004003d,0x00000006,0x00000071,
-	0x00050057,0x0000000a,0x00000077,0x00000075,0x00000076,0x0003003e,0x00000070,0x00000077,
+	0x00000070,0x0004003d,0x00000007,0x00000072,0x00000009,0x00050050,0x00000007,0x00000073,
-	0x000100fd,0x00010038
+	0x00000071,0x00000071,0x00050088,0x00000007,0x00000074,0x00000072,0x00000073,0x0003003e,
+	0x00000009,0x00000074,0x0004003d,0x00000078,0x0000007b,0x0000007a,0x0004003d,0x00000007,
+	0x0000007c,0x00000009,0x00050057,0x0000000a,0x0000007d,0x0000007b,0x0000007c,0x0003003e,
+	0x00000076,0x0000007d,0x000100fd,0x00010038
 };

src/client/refresh/vk/vk_common.c

@@ -1938,6 +1938,7 @@ VkResult QVk_BeginFrame(const VkViewport* viewport, const VkRect2D* scissor)
 {
 	// reset tracking variables
 	vk_state.current_pipeline = VK_NULL_HANDLE;
+	vk_state.current_renderpass = RP_COUNT;
 	vk_config.vertex_buffer_usage  = 0;
 	// triangle fan index buffer data will not be cleared between frames unless the buffer itself is too small
 	vk_config.index_buffer_usage   = vk_triangleFanIboUsage;
@@ -2115,6 +2116,7 @@ void QVk_BeginRenderpass(qvkrenderpasstype_t rpType)
 	}
 
 	vkCmdBeginRenderPass(vk_commandbuffers[vk_activeBufferIdx], &renderBeginInfo[rpType], VK_SUBPASS_CONTENTS_INLINE);
+	vk_state.current_renderpass = rpType;
 }
 
 #if 0

src/client/refresh/vk/vk_pipeline.c

@@ -166,7 +166,7 @@ void QVk_CreatePipeline(const VkDescriptorSetLayout *descriptorLayout, const uin
 		{
 			.stageFlags = VK_SHADER_STAGE_FRAGMENT_BIT,
 			.offset = 17 * sizeof(float),
-			.size = 4 * sizeof(float)
+			.size = 5 * sizeof(float)
 	}};
 
 	VkPipelineLayoutCreateInfo plCreateInfo = {

src/client/refresh/vk/vk_rmain.c

@@ -104,6 +104,7 @@ cvar_t	*r_lockpvs;
 cvar_t	*vk_polyblend;
 cvar_t	*r_modulate;
 cvar_t	*vk_shadows;
+cvar_t	*vk_pixel_size;
 cvar_t	*vk_particle_size;
 cvar_t	*vk_particle_att_a;
 cvar_t	*vk_particle_att_b;
@@ -540,7 +541,9 @@ void R_DrawParticles (void)
 			float att_c;
 		} particleUbo;
 
-		particleUbo.particleSize = vk_particle_size->value;
+		// Particle size needs to be scaled down proportionally to vk_pixel_size.
+		const float divisor = (vk_pixel_size->value < 1.0f ? 1.0f : vk_pixel_size->value);
+		particleUbo.particleSize = vk_particle_size->value / divisor;
 		particleUbo.particleScale = vid.width * ri.Cvar_Get("viewsize", "100", CVAR_ARCHIVE)->value / 102400;
 		particleUbo.minPointSize = vk_particle_min_size->value;
 		particleUbo.maxPointSize = vk_particle_max_size->value;
@@ -871,6 +874,17 @@ R_SetupVulkan (void)
 		.minDepth = 0.f,
 		.maxDepth = 1.f,
 	};
+
+	// When rendering the world, reduce viewport size proportionally to vk_pixel_size.
+	if (vk_state.current_renderpass == RP_WORLD)
+	{
+		const float divisor = (vk_pixel_size->value < 1.0f ? 1.0f : vk_pixel_size->value);
+		viewport.x /= divisor;
+		viewport.y /= divisor;
+		viewport.width /= divisor;
+		viewport.height /= divisor;
+	}
+
 	vkCmdSetViewport(vk_activeCmdbuffer, 0, 1, &viewport);
 
 	// set up projection matrix
@@ -930,6 +944,16 @@ static void RE_RenderView (refdef_t *fd)
 		.extent = { r_newrefdef.width, r_newrefdef.height }
 	};
 
+	// When rendering the world, scale down scissor proportionally to vk_pixel_size.
+	if (vk_state.current_renderpass == RP_WORLD)
+	{
+		const float divisor = (vk_pixel_size->value < 1.0f ? 1.0f : vk_pixel_size->value);
+		scissor.offset.x /= divisor;
+		scissor.offset.y /= divisor;
+		scissor.extent.width /= divisor;
+		scissor.extent.height /= divisor;
+	}
+
 	vkCmdSetScissor(vk_activeCmdbuffer, 0, 1, &scissor);
 
 	R_PushDlights();
@@ -986,13 +1010,25 @@ qboolean RE_EndWorldRenderpass(void)
 	// finish rendering world view to offsceen buffer
 	vkCmdEndRenderPass(vk_activeCmdbuffer);
 
-	// apply postprocessing effects (underwater view warp if the player is submerged in liquid) to offscreen buffer
+	// apply postprocessing effects to offscreen buffer:
+	//	* underwater view warp if the player is submerged in liquid
+	//	* restore world view to the full screen size when vk_pixel_size is >1.0
 	QVk_BeginRenderpass(RP_WORLD_WARP);
-	float pushConsts[] = { (r_newrefdef.rdflags & RDF_UNDERWATER) ? r_newrefdef.time : 0.f, viewsize->value / 100, vid.width, vid.height };
+	float pushConsts[] =
+	{
+		(r_newrefdef.rdflags & RDF_UNDERWATER) ? r_newrefdef.time : 0.f,
+		viewsize->value / 100.0f,
+		vid.width,
+		vid.height,
+		(vk_pixel_size->value < 1.0f ? 1.0f : vk_pixel_size->value),
+	};
 	vkCmdPushConstants(vk_activeCmdbuffer, vk_worldWarpPipeline.layout,
 		VK_SHADER_STAGE_FRAGMENT_BIT, 17 * sizeof(float), sizeof(pushConsts), pushConsts);
 	vkCmdBindDescriptorSets(vk_activeCmdbuffer, VK_PIPELINE_BIND_POINT_GRAPHICS, vk_worldWarpPipeline.layout, 0, 1, &vk_colorbuffer.descriptorSet, 0, NULL);
 	QVk_BindPipeline(&vk_worldWarpPipeline);
+	// Restore full viewport for future steps.
+	vkCmdSetViewport(vk_activeCmdbuffer, 0u, 1u, &vk_viewport);
+	vkCmdSetScissor(vk_activeCmdbuffer, 0u, 1u, &vk_scissor);
 	vkCmdDraw(vk_activeCmdbuffer, 3, 1, 0, 0);
 	vkCmdEndRenderPass(vk_activeCmdbuffer);
 
@@ -1159,6 +1195,7 @@ R_Register( void )
 	vk_polyblend = ri.Cvar_Get("vk_polyblend", "1", 0);
 	r_modulate = ri.Cvar_Get("r_modulate", "1", CVAR_ARCHIVE);
 	vk_shadows = ri.Cvar_Get("vk_shadows", "0", CVAR_ARCHIVE);
+	vk_pixel_size = ri.Cvar_Get("vk_pixel_size", "1", CVAR_ARCHIVE);
 	vk_particle_size = ri.Cvar_Get("vk_particle_size", "40", CVAR_ARCHIVE);
 	vk_particle_att_a = ri.Cvar_Get("vk_particle_att_a", "0.01", CVAR_ARCHIVE);
 	vk_particle_att_b = ri.Cvar_Get("vk_particle_att_b", "0.0", CVAR_ARCHIVE);

stuff/shaders/world_warp.frag

@@ -1,7 +1,8 @@
 #version 450
 #extension GL_ARB_separate_shader_objects : enable
 
-// Underwater screen warp effect similar to what software renderer provides
+// Underwater screen warp effect similar to what software renderer provides.
+// Pixel size to simulate lower screen resolutions is used to restore world to full screen size.
 
 layout(push_constant) uniform PushConstant
 {
@@ -9,6 +10,7 @@ layout(push_constant) uniform PushConstant
 	layout(offset = 72) float scale;
 	layout(offset = 76) float scrWidth;
 	layout(offset = 80) float scrHeight;
+	layout(offset = 84) float pixelSize;
 } pc;
 
 layout(set = 0, binding = 0) uniform sampler2D sTexture;
@@ -32,5 +34,7 @@ void main()
 		uv += distortion;
 	}
 
+	uv /= pc.pixelSize;
+
 	fragmentColor = texture(sTexture, uv);
 }