Motion blur pass.

raw/motion_blur_pass/motion_blur_pass.frag.glsl

@@ -1,3 +1,5 @@
+// Based on GPU Gems 3
+// http://http.developer.nvidia.com/GPUGems3/gpugems3_ch27.html
 #version 450
 
 #ifdef GL_ES
@@ -10,19 +12,70 @@ uniform sampler2D gbuffer2;
 
 uniform sampler2D tex;
 uniform mat4 prevVP;
+uniform mat4 invVP;
 
 in vec2 texCoord;
 
-void main() {
-	vec4 col = texture(tex, texCoord);
+vec2 getVelocity(vec2 texCoord, float depth) {
+	// Get the depth buffer value at this pixel  
+	float zOverW = depth;
+	// H is the viewport position at this pixel in the range -1 to 1
+	vec4 H = vec4(texCoord.x * 2.0 - 1.0, (texCoord.y) * 2.0 - 1.0, zOverW, 1.0);  
+	// Transform by the view-projection inverse
+	vec4 D = invVP * H;  
+	// Divide by w to get the world position
+	vec4 worldPos = D / D.w;
 	
-	vec4 g0 = texture(gbuffer0, texCoord);
-	vec4 g1 = texture(gbuffer0, texCoord);
-	float depth = g0.a;
-    // vec3 p = getViewPos(texCoord, depth);
-    vec3 p = g1.rgb * 2.0 - 1.0;
-	
-
-	
-	gl_FragColor = col;
+	// Current viewport position
+	vec4 currentPos = H;
+	// Use the world position, and transform by the previous view-projection matrix
+	vec4 previousPos = prevVP * worldPos;
+	previousPos /= previousPos.w;
+	// Use this frame's position and last frame's to compute the pixel velocity
+	vec2 velocity = (currentPos - previousPos).xy / 40.0;
+	return velocity;
+}
+
+void main() {	
+	vec4 g0 = texture(gbuffer0, texCoord);
+	float depth = g0.a;
+
+	float blurScale = 1.0; //currentFps / targeFps;
+	vec2 velocity = getVelocity(texCoord, depth) * blurScale;
+	
+	const int samples = 8;  
+	vec4 color = texture(tex, texCoord);
+	vec2 offset = texCoord;
+	// for(int i = 1; i < samples; ++i) {
+		// Sample the color buffer along the velocity vector
+		// offset += velocity;  
+   		// color += texture(tex, offset);  
+		
+		offset += velocity;  
+   		color += texture(tex, offset);  
+
+		offset += velocity;  
+   		color += texture(tex, offset);  
+		
+		offset += velocity;  
+   		color += texture(tex, offset);  
+		
+		offset += velocity;  
+   		color += texture(tex, offset);  
+		
+		offset += velocity;  
+   		color += texture(tex, offset);  
+		
+		offset += velocity;  
+   		color += texture(tex, offset);  
+		
+		offset += velocity;  
+   		color += texture(tex, offset);  
+		
+		offset += velocity;  
+   		color += texture(tex, offset);  
+	// }
+	
+	vec4 finalColor = color / samples; 
+	gl_FragColor = finalColor;
 }

raw/motion_blur_pass/motion_blur_pass.shader.json

@@ -28,6 +28,10 @@
 				{
 					"id": "prevVP",
 					"link": "_prevViewProjectionMatrix"
+				},
+				{
+					"id": "invVP",
+					"link": "_inverseViewProjectionMatrix"
 				}
 			],
 			"texture_params": [],