CODEWITHSUNDEEP
c++opengl
mikestaub
mikestaub

Reputation: 2173

What's wrong with my usage of glBindTexture?

I am rendering a chess board, using 2 different textures. One for the black squares and one for the white squares. However instead of each different square having their own texture, they all take on the last texture that I bound calling glBindTexture(GL_TEXTURE_2D, id);.

This is my approach: 

glEnable(GL_TEXTURE_2D);    
glBegin(GL_QUADS);
    // square 0, 0 ( front left )
    glBindTexture(GL_TEXTURE_2D, textureBlackSquare->texID);
    glNormal3f(0, 1, 0);
    glTexCoord2f(0, 0); glVertex3f(-8.0, 0.5,  8.0);
    glTexCoord2f(1, 0); glVertex3f(-6.0, 0.5,  8.0);
    glTexCoord2f(1, 1); glVertex3f(-6.0, 0.5,  6.0);
    glTexCoord2f(0, 1); glVertex3f(-8.0, 0.5,  6.0);
glEnd();

glBegin(GL_QUADS);
    // square 1, 0        
    glBindTexture(GL_TEXTURE_2D, textureWhiteSquare->texID);
    glTexCoord2f(0, 0); glVertex3f(-6.0, 0.5,  8.0);
    glTexCoord2f(1, 0); glVertex3f(-4.0, 0.5,  8.0);
    glTexCoord2f(1, 1); glVertex3f(-4.0, 0.5,  6.0);
    glTexCoord2f(0, 1); glVertex3f(-6.0, 0.5,  6.0);
glEnd();

When I run this code, both quads have the white texture bound. How do I get each quad to have its own texture?

Upvotes: 1

Views: 1542

Answers (3)

datenwolf
datenwolf

Reputation: 162164

You can't bind a texture within a glBegin-glEnd block. Also you should avoid switching textures where possible, since switching the texture is among the most expensive things you can ask the GPU to do (a texture switch invalidates all texel fetch caches).

Instead you sort your scene objects by the texture they use and group them by this. So you first render all checkerboard quads using the first texture (say white), and after that all the quads using the second texture (black then).

Upvotes: 2

Lightness Races in Orbit
Lightness Races in Orbit

Reputation: 385098

From the documentation:

GL_INVALID_OPERATION is generated if glBindTexture is executed between the execution of glBegin and the corresponding execution of glEnd.

You forgot to check for errors, and thus missed that your program is invalid.

Upvotes: 3

Nicol Bolas
Nicol Bolas

Reputation: 473212

You cannot call glBindTexture in the middle of glBegin/End. You can only call vertex functions within begin/end.

Also, why don't you just make a single texture as an 8x8 checkerboard, and then just render a single quad to draw the whole checkerboard?

Upvotes: 10

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