Hello everyone, I am trying to implement a simple glow as in the following programs in GLSL: Vertex:

varying vec2 texCoord;

void main()                    
{
   vec2 inPos    = sign(gl_Vertex.xy);
   gl_Position = vec4(inPos.xy, 0.0, 1.0);
   texCoord.x  = 0.5 * ( 1.0 + inPos.x );
   texCoord.y  = 0.5 * ( 1.0 + inPos.y );
}

Fragment:

uniform sampler2D glowTexture;
varying vec2      texCoord;

vec2 offsets[12] = vec2[](
		vec2( -0.326212, -0.405805 ),
		vec2( -0.840144, -0.073580 ),
		vec2( -0.695914,  0.457137 ),
		vec2( -0.203345,  0.620716 ),
		vec2(  0.962340, -0.194983 ),
	    vec2(  0.473434, -0.480026 ),
		vec2(  0.519456,  0.767022 ),
		vec2(  0.185461, -0.893124 ),
		vec2(  0.507431,  0.064425 ),
		vec2(  0.896420,  0.412458 ),
		vec2( -0.321940, -0.932615 ),
		vec2( -0.791559, -0.597705 ) );

const float BlurScale = 0.01;

void main()
{
   vec4 sum = texture2D(glowTexture, texCoord);
   
   int i = 0;
   for( i = 0; i < 12; i++ )
   {
      sum += texture2D( glowTexture, texCoord + BlurScale * offsets );
    }
   gl_FragColor = sum / 10.0;
}

Everything works fine except I get the couple line of pixels on the left colored similar to sun. I'm not quite sure why that occurs as also I am not sure why in the original DX implementation (RenderMonkey), the texture coordinates were generated using: texCoord.x = 0.5 * ( 1.0 + inPos.x ); texCoord.y = 0.5 * ( 1.0 - inPos.y ); This gives me a vertically mirrored image as the y coordinate is multiplied by negative. Can someone help me out on this? Thanks. [Edited by - Dynx on November 17, 2008 9:08:53 AM]

The problem was with texture wrapping. When using box filter for blurring, the texture coordinates that are beyond texture limits repeat over the other side therefore for the RTT texture, do:

glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);