Android NDK OpenGL ES 2.0 Texture Pitch

Question

Is there any way to blit a texture in opengl es 2.0 with a pitch that differs from its width. Normally I would fix this by using a PBO or adjusting the GL_PACK_ROW_LENGTH via glPixelStore. However it seems neither GL_PIXEL_UNPACK_BUFFER for binding a buffer to or GL_PACK_ROW_LENGTH exist on the Android platform.

glTex(Sub)Image2D does not support this.

Any tips?

Answer my own question here. In some scenarios this can be solved by adjusting texture coordinates. Lets say I have a 512x512 texture pitched at 512*bitdepth but the data I want to use is pitched to 256*bitdepth. I go ahead and glSubTexImage2D still but adjust the texture coords to be 0 to (256/512) instead of 0 to 1. In other words strip off the part of the texture I'm not using. — Halsafar, Jun 15 '11 at 04:20

score 2 · Answer 1 · edited May 23 '17 at 12:19

2

Quoting @Halsafar

In some scenarios, this can be solved by adjusting texture coordinates.

Lets say I have a 512 x 512 texture pitched at 512 * bitdepth

but the data I want to use is pitched to 256 * bitdepth

I go ahead and glSubTexImage2D still but adjust the texture coords to be 0 to (256/512)

instead of 0 to 1.

In other words strip off the part of the texture I'm not using.

edited May 23 '17 at 12:19

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answered Aug 04 '11 at 15:04

Sherif elKhatib

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Thanks for posting this. I'm sorry I let it die. I've edited my question to clarify. – Halsafar Jan 17 '12 at 07:42

score 1 · Answer 2 · answered Nov 26 '11 at 08:52

it might sound a bit overkill (or even not so fitting to your expectation), but maybe you could simply take advantage of the rasterizer and Frame-buffer objects : create a FBO with the texture as the color buffer and... draw in it some textured quad(s) thanks to a trivial vertex+fragment shader : where you would use a simple Ortho. projection matrix in the vertex shader and use a Point-sampling texture sampling in the fragment shader.

score 0 · Accepted Answer · answered Jan 17 '12 at 07:46

Since I answered it in a comment here is a more direct answer:

// width and height is 256 and max is 512
// texture coordinates
float uMax = (width / max);
float vMax = (height / max);

_texCoords[0] = 0.0; _texCoords[1] =  vMax;
_texCoords[2] = uMax; _texCoords[3] =  vMax;
_texCoords[4] = 0.0; _texCoords[5] =  0.0;
_texCoords[6] = uMax; _texCoords[7] =  0.0;

Now use these texcoords to render and you can stick a 256x256 texture in a 512x512 buffer. The width and height you want to use can be any size equal to or below your max size.

Android NDK OpenGL ES 2.0 Texture Pitch

3 Answers3