Sampler2D vs Sampler2DRect problem

advanced
#1

Can someone explain to me why the following shader works with Sampler2DRect but not with Sampler2D and ofDisableArbTex():

Working shader I can use with normal textures/fbos:

Vertex Shader

void main() {
	gl_TexCoord[0] = gl_MultiTexCoord0;
	gl_Position = ftransform();
}

Fragment Shader

#extension GL_ARB_texture_rectangle : enable

uniform vec2 tcOffset[25];			// offsets
uniform sampler2DRect inputTexture;	// texture

void main() {

	vec4 sample[25];
	vec4 minValue = vec4(1.0);

	for (int i = 0; i < 25; i++) {
		sample[i] = texture2DRect(inputTexture, gl_TexCoord[0].xy + tcOffset[i]);
		minValue = min(sample[i], minValue);
	}

	gl_FragColor = minValue;

}

But even with ofDisableArbTex() this doesn’t work:

uniform vec2 tcOffset[25];			// offsets
uniform sampler2D inputTexture;    	// texture

void main() {

	vec4 sample[25];
	vec4 minValue = vec4(1.0);

	for (int i = 0; i < 25; i++) {
		sample[i] = texture2D(inputTexture, gl_TexCoord[0].xy + tcOffset[i]);
		minValue = min(sample[i], minValue);
	}

	gl_FragColor = minValue;

}

I’m sure this is something mind numbingly simple but I have a bunch of shader examples (more complex than this) I’m trying to get working and they all use Sampler2D…and for the life of me I can’t see why this shouldn’t work.

BTW tcOffsets are calculated with:

// Set up texture sampling offset storage
const GLint tcOffsetColumns = 5;
const GLint tcOffsetRows    = 5;
GLfloat	texCoordOffsets[tcOffsetColumns * tcOffsetRows * 2];

//--------------------------------------------------------------
void genTexCoordOffsets(GLuint width, GLuint height, GLfloat step = 1.0f){
    // Calculate texture coordinate offsets for kernel convolution effects
    // Note: You can multiply the step to displace the samples further. 

    float xInc = step / (GLfloat)(width);
    float yInc = step / (GLfloat)(height);
    
    for (int i = 0; i < tcOffsetColumns; i++)
    {
        for (int j = 0; j < tcOffsetRows; j++)
        {
            texCoordOffsets[(((i*5)+j)*2)+0] = ((-2.0f * xInc) + ((GLfloat)i * xInc)) * width;
            texCoordOffsets[(((i*5)+j)*2)+1] = ((-2.0f * yInc) + ((GLfloat)j * yInc)) * height;
        }
    }
}
#2

Are you also normalising tcOffset[i] when you do ofDisableArbTex()?

#3

Hey hubris

I just edited my post to show how I’m calculating the tcOffsets. How would I normalise these?

#4

I’ve tried just not multiplying by the width and height but still no dice:

			texCoordOffsets[(((i * 5) + j) * 2) + 0] = ((-2.0f * xInc) + ((GLfloat)i * xInc));// *width;
			texCoordOffsets[(((i * 5) + j) * 2) + 1] = ((-2.0f * yInc) + ((GLfloat)j * yInc));// *height;
#5

Something like that should suffice. Can you post the rest your code? Just the bare to replicate your issue.

Also, this vec4 sample[25] variable it’s not doing much. You could just use a vec4 or place the sampling of the texture directly inside the min function.