Scale point size to match camera distance, base point size on particle mass

computenbody/computenbody.cpp

@@ -27,7 +27,7 @@
 // Lower particle count on Android for performance reasons
 #define PARTICLES_PER_ATTRACTOR 2 * 1024
 #else
-#define PARTICLES_PER_ATTRACTOR 8 * 1024
+#define PARTICLES_PER_ATTRACTOR 4 * 1024
 #endif
 
 class VulkanExample : public VulkanExampleBase
@@ -56,6 +56,7 @@ public:
 		struct {
 			glm::mat4 projection;
 			glm::mat4 view;
+			glm::vec2 screenDim;
 		} ubo;
 	} graphics;
 
@@ -371,7 +372,7 @@ public:
 			vkTools::initializers::vertexInputAttributeDescription(
 				VERTEX_BUFFER_BIND_ID,
 				0,
-				VK_FORMAT_R32G32B32_SFLOAT,
+				VK_FORMAT_R32G32B32A32_SFLOAT,
 				offsetof(Particle, pos));
 		// Location 1 : Velocity (used for gradient lookup)
 		vertices.attributeDescriptions[1] =
@@ -703,6 +704,7 @@ public:
 	{
 		graphics.ubo.projection = camera.matrices.perspective;
 		graphics.ubo.view = camera.matrices.view;
+		graphics.ubo.screenDim = glm::vec2((float)width, (float)height);
 		memcpy(graphics.uniformBuffer.mapped, &graphics.ubo, sizeof(graphics.ubo));
 	}
 

data/shaders/computenbody/particle.vert

@@ -3,7 +3,7 @@
 #extension GL_ARB_separate_shader_objects : enable
 #extension GL_ARB_shading_language_420pack : enable
 
-layout (location = 0) in vec3 inPos;
+layout (location = 0) in vec4 inPos;
 layout (location = 1) in vec4 inVel;
 
 layout (location = 0) out float outGradientPos;
@@ -12,6 +12,7 @@ layout (binding = 2) uniform UBO
 {
 	mat4 projection;
 	mat4 modelview;
+	vec2 screendim;
 } ubo;
 
 out gl_PerVertex
@@ -23,6 +24,14 @@ out gl_PerVertex
 void main () 
 {
 	gl_PointSize = 8.0;	
+
+	const float spriteSize = 0.005 * inPos.w; // Point size influenced by mass (stored in inPos.w);
+
+	vec4 eyePos = ubo.modelview * vec4(inPos.x, inPos.y, inPos.z, 1.0); 
+	vec4 projectedCorner = ubo.projection * vec4(0.5 * spriteSize, 0.5 * spriteSize, eyePos.z, eyePos.w);
+	gl_PointSize = ubo.screendim.x * projectedCorner.x / projectedCorner.w;
+	
+	gl_Position = ubo.projection * eyePos;
+
 	outGradientPos = inVel.w;
-	gl_Position = ubo.projection * ubo.modelview * vec4(inPos, 1.0);
 }