Question

I am using GL Kit to draw a cube which rotates on the screen. I have this working very well with the same texture drawn on each face. I would like to draw a different texture on each face.

This is currently how my code draws the cube (note that I actually have 6 different textures loaded in the theTextures array, but so far I only draw all the sides of the cube the same when I change textures).

self.effect.texture2d0.name = theTextures[i].name;
self.effect.texture2d0.enabled = true;
self.effect.texture2d0.target = GLKTextureTarget2D;

glBindBuffer(GL_ARRAY_BUFFER, _vertexBuffer);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, _indexBuffer);

glBindVertexArrayOES(_vertexArray); 

glDrawElements(GL_TRIANGLES, sizeof(Indices)/sizeof(Indices[0]), GL_UNSIGNED_BYTE, 0);

I have done a lot of searches here on stackOverflow and looked at many tutorials, but can’t find a simple way to do this. I assume that I can create a vertex array for each of the sides and use glDrawElements for each vertex array, but that seems very inefficient. Is there a way for me to do this without having to create 6 different vertex arrays? Thanks!

Answer 1

I found away to do this in a somewhat efficient way, although I still draw each side separately. I create a different vertex array & texture for each side, but use only one Indice array with the vertices described in two triangles. If you have any suggestions, please send them my way,

// draw one texture per side

for (int i = 0; i <= 5; i++)
{
    glBindBuffer(GL_ARRAY_BUFFER, _vertexBuffer[i]);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, _indexBuffer);

    glEnableVertexAttribArray(GLKVertexAttribPosition);
    glVertexAttribPointer(GLKVertexAttribPosition, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid *) offsetof(Vertex, Position));
    glEnableVertexAttribArray(GLKVertexAttribColor);
    glVertexAttribPointer(GLKVertexAttribColor, 4, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid *) offsetof(Vertex, Color));
    glEnableVertexAttribArray(GLKVertexAttribTexCoord0);
    glVertexAttribPointer(GLKVertexAttribTexCoord0, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid *) offsetof(Vertex, TexCoord));

    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, myTexture[i].name);

    glDrawElements(GL_TRIANGLES, sizeof(Indices1)/sizeof(Indices1[0]), GL_UNSIGNED_BYTE, 0);
}