OpenGL rendering white texture bug

Question

I use OpenGL and SDL2 to render spine animations. In a specific z-order this animations are disposed like white blocks. All texture get white. I guess this error is in OpenGL draw code.

glPushMatrix();

float texw=0, texh=0;
if (texture) {
    glEnableClientState(GL_TEXTURE_COORD_ARRAY);
    if (SDL_GL_BindTexture(texture, &texw, &texh) != 0)
        printf("WTF\n");
}

glEnableClientState(GL_VERTEX_ARRAY);
glColor4f(color[0], color[1], color[2], color[3]);

glVertexPointer(2, GL_FLOAT, 0, vertices);


glTexCoordPointer(2, GL_FLOAT, 0, uvs);

glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

// if (num_vertices > 0) {
glDrawElements(GL_TRIANGLES, num_indices, GL_UNSIGNED_SHORT, indices);

glDisableClientState(GL_VERTEX_ARRAY);
// glDisableClientState(GL_COLOR_ARRAY);


if (texture) {
    SDL_GL_UnbindTexture(texture);
    glDisableClientState(GL_TEXTURE_COORD_ARRAY);
}

glColor4f(1.0, 1.0, 1.0, 1.0);
glPopMatrix();

This is my code, some one see something wrong in this code ? Why i'm getting white textures ?

What are those `SDL_GL_BindTexture()`/`SDL_GL_UnbindTexture()` calls (which take `SDL_Texture`s, not `GLuint`s) doing in there? Assuming `texture` is a `GLuint` like `glGenTextures()` requires, how'd that even *compile*? Edit in a [mcve]. — genpfault, Dec 09 '20 at 19:21

Rabbid76 · Answer 1 · 2020-12-09T18:09:18.340

0

Two-dimensional texturing has to be enabled by glEnable(GL_TEXTURE_2D) and can be disabled by glDisable(GL_TEXTURE_2D).
If texturing is enables then the texture wich is currently bound when the geometry is drawn is wrapped on the geometry.

If texturing is enabled, then by default the color of the texel is multiplied by the current color, because by default the texture environment mode (GL_TEXTURE_ENV_MODE) is GL_MODULATE. See glTexEnv. This causes that the color of the texels of the texture is "mixed" by the last color which you have set by glColor4f.

glEnable(GL_TEXTURE_2D);
glDrawElements(GL_TRIANGLES, num_indices, GL_UNSIGNED_SHORT, indices);
glDisable(GL_TEXTURE_2D);

Note that all of this only applies in immediate mode if you are not using a shader program.

edited Dec 09 '20 at 18:09

answered Dec 09 '20 at 18:02

Rabbid76

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Thank you Rabbid76, I tried to use your tip, but nothing has changed. The white blocks are still on the screen :( – Jonas Forte Dec 09 '20 at 18:24
@JonasForte So there is another bug somewhere else in your code. – Rabbid76 Dec 09 '20 at 18:29
Do you think the bug isn't in this code ? – Jonas Forte Dec 09 '20 at 18:34
@JonasForte If texturing is enabled, the the quads can't be white, except the texture itself is white. – Rabbid76 Dec 09 '20 at 18:36

OpenGL rendering white texture bug

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