Jump to content
  • Advertisement
Sign in to follow this  
ARB1130

How to get texture u v value?

This topic is 4489 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

Hi! I have a simple question: I set a texture in 2x2 size. I want to get the u v value.In fact,it should be 0.0,0.5 and 1.0 in uv but I got 0.25 and 0.75 Please tell me how to get them or some tip! thank you! ^_^ my code is: ////////////////////////////////// //my fragment void main() { float u=gl_TexCoord[0].x; gl_FragColor =vec4(u,u,u,u); } ////////////////////////////////// //texture parameter set glGenTextures(1, &_iTexture); glBindTexture(GL_TEXTURE_2D, _iTexture); glTexParameteri(GL_TEXTURE_RETANGLE_NV, GL_TEXTURE_MIN_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_RETANGLE_NV, GL_TEXTURE_MAG_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_RETANGLE_NV, GL_TEXTURE_WRAP_S, GL_CLAMP); glTexParameteri(GL_TEXTURE_RETANGLE_NV, GL_TEXTURE_WRAP_T, GL_CLAMP); glTexImage2D(GL_TEXTURE_RETANGLE_NV, 0,GL_FLOAT_RGBA32_NV,_iWidth,_iHeight,0, GL_RGBA, GL_FLOAT, 0); ///////////////////////////////// //Viewport-Sized Quad = Data Stream Generator glBegin(GL_QUADS); { glTexCoord2f(0, 0); glVertex3f(-1, -1, -0.5f); glTexCoord2f(1, 0); glVertex3f( 1, -1, -0.5f); glTexCoord2f(1, 1); glVertex3f( 1, 1, -0.5f); glTexCoord2f(0, 1); glVertex3f(-1, 1, -0.5f); } glEnd(); //////////////////////////////// //1:1 pixel to texture mapping glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluOrtho2D(-1, 1, -1, 1); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); ////////////////////////////////

Share this post


Link to post
Share on other sites
Advertisement
Where do you "get" any value at all? Right now, all I can see is some rendering code. What specific spot do you want to "get" the values from?

In OpenGL, both display pixels and texture pixels (texels) are measured with 0,0 at the edge. Thus, the center of a texel is at 0.25 and 0.75 in a two-pixel texture, and the center of a display pixel is at 0.5 and 1.5 in a two-pixel display area. Texture sampling is done at the center of each pixel, so if you draw a rectangle from 0 to 2, it will sample at 0.5 and 1.5.

Share this post


Link to post
Share on other sites
Thank you for your response!

So if I ues the glReadPixels( 0, 0, 2, 2, GL_RED, GL_FLOAT, array );

I can get two values about the center of the texels.

0.25 and 0.75 .

so if I use the "vec4 c = texture2D(texUnit, texCoord.st);"

I can get the value which is interpolated near two value replacing ,is it

right?

^_^

Share this post


Link to post
Share on other sites
Sign in to follow this  

  • Advertisement
×

Important Information

By using GameDev.net, you agree to our community Guidelines, Terms of Use, and Privacy Policy.

We are the game development community.

Whether you are an indie, hobbyist, AAA developer, or just trying to learn, GameDev.net is the place for you to learn, share, and connect with the games industry. Learn more About Us or sign up!

Sign me up!