GLTextureFilter. How to hook up a the xml correctly to the glsl shader?

mr.t

GLTextureFilter. How to hook up a the xml correctly to the glsl shader?

in Contributed Library Questions • 1 year ago

Dear Forum,

I must admit that I am a complete rooky with shaders.
But for a project i need a blur shader due to performance reasons with variable radius to control the blur intensity.

So I found this nice fragment shader which works smooth with processing 2.0

// Adapted from:
// http://callumhay.blogspot.com/2010/09/gaussian-blur-shader-glsl.html
uniform sampler2D textureSampler;
// The inverse of the texture dimensions along X and Y
uniform vec2 texcoordOffset;
varying vec4 vertColor;
varying vec4 vertTexcoord;
uniform int blurSize;
uniform int horizontalPass; // 0 or 1 to indicate vertical or horizontal pass
uniform float sigma; // The sigma value for the gaussian function: higher value means more blur
// A good value for 9x9 is around 3 to 5
// A good value for 7x7 is around 2.5 to 4
// A good value for 5x5 is around 2 to 3.5
// ... play around with this based on what you need :)
const float pi = 3.14159265;
void main() {
float numBlurPixelsPerSide = float(blurSize / 2);
vec2 blurMultiplyVec = 0 < horizontalPass ? vec2(1.0, 0.0) : vec2(0.0, 1.0);
// Incremental Gaussian Coefficent Calculation (See GPU Gems 3 pp. 877 - 889)
vec3 incrementalGaussian;
incrementalGaussian.x = 1.0 / (sqrt(2.0 * pi) * sigma);
incrementalGaussian.y = exp(-0.5 / (sigma * sigma));
incrementalGaussian.z = incrementalGaussian.y * incrementalGaussian.y;
vec4 avgValue = vec4(0.0, 0.0, 0.0, 0.0);
float coefficientSum = 0.0;
// Take the central sample first...
avgValue += texture2D(textureSampler, vertTexcoord.st) * incrementalGaussian.x;
coefficientSum += incrementalGaussian.x;
incrementalGaussian.xy *= incrementalGaussian.yz;
// Go through the remaining 8 vertical samples (4 on each side of the center)
for (float i = 1.0; i <= numBlurPixelsPerSide; i++) {
avgValue += texture2D(textureSampler, vertTexcoord.st - i * texcoordOffset *
blurMultiplyVec) * incrementalGaussian.x;
avgValue += texture2D(textureSampler, vertTexcoord.st + i * texcoordOffset *
blurMultiplyVec) * incrementalGaussian.x;
coefficientSum += 2.0 * incrementalGaussian.x;
incrementalGaussian.xy *= incrementalGaussian.yz;
}
gl_FragColor = avgValue / coefficientSum;
}

But I need to stick with Processing 1.5.1 for now.
So by looking at the GLTexture examples I tried to write the correct xml for this.

<filter name="blur">
<description>Blur filter</description>
<vertex>SimpleVS.glsl</vertex>
<fragment>Blur.glsl</fragment>
<textures input="1" output="1">
<intexture type="sampler2d" name="textureSampler" label="Texture from which to blur">0</intexture>
</textures>
<parameters>
<parameter type="int" name="blurSize" label="Blur Size">5</parameter>
<parameter type="int" name="horizontalPass" label="horizontal Pass ">0</parameter>
<parameter type="float" name="sigma" label="Sigma">2.3</parameter>
</parameters>
</filter>

And calling it all like:

import processing.opengl.*;
import codeanticode.glgraphics.*;
size(256, 256, GLConstants.GLGRAPHICS);
GLTexture tex0 = new GLTexture(this, "lights.jpg");
GLTexture tex2 = new GLTexture(this, 256, 256);
GLTextureFilter blurFilter = new GLTextureFilter(this, "Blur.xml");
blurFilter.setParameterValue("blurSize", 10);
blurFilter.apply(tex0, tex2);
image(tex2, 0, 0);

which throws me a bunch of crasy errors:

Fragment shader Blur.glsl compilation:
ERROR: 0:38: Use of undeclared identifier 'textureSampler'
ERROR: 0:44: Use of undeclared identifier 'textureSampler'
ERROR: 0:46: Use of undeclared identifier 'textureSampler'

GLSL program validation:
Validation Failed: Link error:
Program is not successfully linked.

Error in filter parameter blurSize: no valid opengl ID.
Error in filter parameter horizontalPass: no valid opengl ID.
Error in filter parameter sigma: no valid opengl ID.
OpenGL error 1282 at render_triangles in: invalid operation

I am probably doing something fundamently wrong.
But don't know where to look.

So, dear forum, can you point me into the right direction?

Replies(5)

thomashol..

Re: GLTextureFilter. How to hook up a the xml correctly to the glsl shader?

1 year ago

Try calling your texture "textureSampler0".

Or else, you can remove the <intexture>... </intexture> and change the variable name of your texture to "src_tex_unit0" instead of "textureSampler"

mr.t

Re: GLTextureFilter. How to hook up a the xml correctly to the glsl shader?

1 year ago

ok. thanx thomas!

this fixed the texture issue. but I still get these errors for the parameters:

GLSL program validation:
Validation Failed: Link error:
Program is not successfully linked.

Error in filter parameter blurSize: no valid opengl ID.
Error in filter parameter horizontalPass: no valid opengl ID.
Error in filter parameter sigma: no valid opengl ID.
OpenGL error 1282 at render_triangles in: invalid operation

Is there any documentation how to map the xml and glsl file?

thomashol..

Re: GLTextureFilter. How to hook up a the xml correctly to the glsl shader?

1 year ago

I suspect that the problem is with the variables declared at the top:

uniform vec2 texcoordOffset;
varying vec4 vertColor;
varying vec4 vertTexcoord;

You can get rid of varying vec4 vertColor; since that is not used in the shader. The texture coordinates are typically available as gl_TexCoord[0].st so you don't need the vertTexcoord. As far as the offset, unless it is generated by your vertex shader, it isn't getting initialized. I suspect you may want to use the glsl textureSize2D() function to get that value.

In general, any variables outside a function (attributes, I think they are called) are either passed in from the vertex shader or the xml file.

mr.t

Re: GLTextureFilter. How to hook up a the xml correctly to the glsl shader?

1 year ago

Ok. So far so good besides the offset.

Which seems to be a processing 2.0 fixed variable.

texcoordOffset (vec2): inverse of the texture resolution (displacement in normalized coords from one texel to the next)

But how would i get this on my own?
With texture2d I had no luck. I tried calling:

texcoordOffset = textureSize2D(textureSampler0,0);

like i found on the interwebs but it keeps telling me:

call to undeclared function 'textureSize2D'

mr.t

Re: GLTextureFilter. How to hook up a the xml correctly to the glsl shader?

1 year ago

Ha!

Looking at the GLTextureFilter examples again I found the solution:

In the xml we do need the intexture but like this:

<textures input="1" output="1">
<intexture type="sampler2d" name="textureSampler" offset="texcoordOffset" label="Input image">0</intexture>
</textures>

in the fragment shader:

vec4 vertColor we can remove.
and instead of vertTexcoord we use gl_TexCoord[0].st as described by thomas.

et voila !

UPDATE:
and who ever is looking for it too: here s the reference:
http://codeanticode.wordpress.com/2008/03/31/gltexture-library-for-processing/

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