Enabled motion blur shader in split screen multiplayer.

git-svn-id: svn+ssh://svn.code.sf.net/p/supertuxkart/code/main/trunk@12552 178a84e3-b1eb-0310-8ba1-8eac791a3b58

data/shaders/motion_blur.frag

@@ -1,17 +1,26 @@
 // motion_blur.frag
 
-uniform float boost_amount;	// should be in the range [0.0, 1.0]
+// The actual boost amount (which linearly scales the blur to be shown).
+// should be in the range [0.0, 1.0], though a larger value might make
+// the blurring too string. Atm we are using [0, 0.5].
+uniform float boost_amount;
+
+// The color buffer to use.
 uniform sampler2D color_buffer;
 
-// The blur direction points to the following center (we work in [0, 1]x[0, 1] coordinates):
-#define BLUR_DIR_CENTER vec2(0.5, 0.7)
+// Center (in texture coordinates) at which the kart is. A small circle
+// around this center is not blurred (see mask_radius below)
+uniform vec2 center;
 
-// There is a mask around the character so that it doesn't get blurred
-#define BLUR_MASK_CENTER vec2(0.5, 0.2)
-#define BLUR_MASK_RADIUS 0.15
+// The direction to which the blurring aims at
+uniform vec2 direction;
 
-// Final scaling factor
-#define BLUR_SCALE 0.2
+// Radius of mask around the character in which no blurring happens 
+// so that the kart doesn't get blurred.
+uniform float mask_radius;
+
+// Maximum height of texture used
+uniform float max_tex_height;
 
 // Number of samples used for blurring
 #define NB_SAMPLES 12
@@ -23,24 +32,29 @@ void main()
 	// Sample the color buffer
 	vec3 color = texture2D(color_buffer, texcoords).rgb;
 	
+	// If no motion blur is needed, don't do any of the blur computation,
+	// just return the color from the texture.
+	if(boost_amount==0)
+	{
+		gl_FragColor = vec4(color, 1.0);
+		return;
+	}
+	
 	// Compute the blur direction.
-	// IMPORTANT: we don't normalize it so that it avoids a glitch around BLUR_DIR_CENTER,
+	// IMPORTANT: we don't normalize it so that it avoids a glitch around 'center',
 	// plus it naturally scales the motion blur in a cool way :)
-	vec2 blur_dir = BLUR_DIR_CENTER - texcoords;
+	vec2 blur_dir = direction - texcoords;
 	
 	// Compute the blurring factor:
-	// - apply the mask
-	float blur_factor = max(0.0, length(texcoords - BLUR_MASK_CENTER) - BLUR_MASK_RADIUS);
+	// - apply the mask, i.e. no blurring in a small circle around the kart
+	float blur_factor = max(0.0, length(texcoords - center) - mask_radius);
 	
 	// - avoid blurring the top of the screen
-	blur_factor *= (1.0-texcoords.t);
+	blur_factor *= (max_tex_height - texcoords.t);
 	
 	// - apply the boost amount
 	blur_factor *= boost_amount;
 	
-	// - apply a final scaling factor
-	blur_factor *= BLUR_SCALE;
-	
 	// Scale the blur direction
 	blur_dir *= blur_factor;
 	
@@ -56,5 +70,5 @@ void main()
 	gl_FragColor = vec4(color, 1.0);
 
 	// Keep this commented line for debugging:
-//	gl_FragColor = vec4(blur_factor, blur_factor, blur_factor, 0.0);
+	//gl_FragColor = vec4(blur_factor, blur_factor, blur_factor, 0.0);
 }

data/shaders/motion_blur.vert

@@ -2,6 +2,6 @@
 
 void main()
 {
-	gl_TexCoord[0].st = vec2(gl_MultiTexCoord0.s, 1.0-gl_MultiTexCoord0.t);
+	gl_TexCoord[0].st = vec2(gl_MultiTexCoord0.s, gl_MultiTexCoord0.t);
 	gl_Position = gl_Vertex;
 }