Hey there, I'm trying to code in C++ a mesh with VBO, I already have the vertex, normals and the indices, with a bit of code using functions like these:



glGenBuffers(NUM_BUFFERS, sfm->buffers);

//vertex
glBindBuffer(GL_ARRAY_BUFFER, sfm->buffers[VERTICES]);
glBufferData(GL_ARRAY_BUFFER, sfm->numOfVertexes*sizeof(float)*FLOATS_PER_VERTEX, sfm->verte, GL_STATIC_DRAW);
glVertexPointer(3,GL_FLOAT,0,BUFFER_OFFSET(0));
glEnableClientState(GL_VERTEX_ARRAY);

//normals
glBindBuffer(GL_ARRAY_BUFFER, sfm->buffers[NORMALS]);
glBufferData(GL_ARRAY_BUFFER, sfm->numOfNormals*sizeof(float)*FLOATS_PER_NORMAL, sfm->normals, GL_STATIC_DRAW);
glNormalPointer(GL_FLOAT,0,BUFFER_OFFSET(0));
glEnableClientState(GL_NORMAL_ARRAY);

glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, sfm->buffers[INDICES]);
glBufferData(GL_ELEMENT_ARRAY_BUFFER,sfm->numOfIndices*sizeof(int) ,sfm->indices, GL_STATIC_DRAW);



but I found a "half-problem", I was searching and found the function "glTexCoordPointer" which I can use to add to my VBO the texture coordinates with some more functions like in the code above, the problem here is that I can't find any functions that change my texture, sometimes I might want to use a different texture in some of parts of my mesh.

I call this a "half-problem" because I think I can create a very big texture for the whole mesh, but I would like to know if there is a way to change my texture when I'm drawing the mesh, is it possible or do I have to use the giant texture idea?

Thanks for the help,

[color=#1C2837][size=2]texture atlas was what I was thinking when I talked about the big texture, texture arrays from what I saw is a good solution, but I can't find good documentation about it and I still haven't found anything in my openGL book that describes it well, and from what i read, texture arrays can only be used in nvidia 8x00+ graphics cards, and I assume in ati/amd equivalent cards.
[color=#1C2837][size=2]

[color=#1C2837][size=2]I'm making a tower defense game, so I'm using a mesh with square zones (each square is made of 2 triangles), so I think I can render 2 triangles and after that change my texture and render other too, and continue this cycle until I complete my rendering function.

Thanks for the help,

[color="#1C2837"]texture atlas was what I was thinking when I talked about the big texture, texture arrays from what I saw is a good solution, but I can't find good documentation about it and I still haven't found anything in my openGL book that describes it well.

This is some code I put together quickly from when I was learning to do this.



glGenTextures(1, &yourtextureid);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, yourtextureid);

//create a TEXTURE_2D_ARRAY, making sure the texture width and height are the dimensions of your largest texture.
//The last argument is NULL as we want to iterate through our images and put them in the correct position in our texture array using glTexSubImage
glTexImage3D(GL_TEXTURE_2D_ARRAY, 0, internalTextureFormat, textureWidth, textureHeight, numberOfTextures, 0, textureFormat, GL_UNSIGNED_BYTE, NULL);

//iterate through the images to put into your texture array
glTexSubImage3D(GL_TEXTURE_2D_ARRAY, 0, 0, 0, i, image.width, image.height, 1, textureFormat, GL_UNSIGNED_BYTE, image.pixelData);

#version 420 core
uniform sampler2DArray myTextureSampler;
in vec2 UV;
in int index;
out vec3 out_Color;

void main(void)
{
//Use the texture coordinates as usual but the different textures are indexed by the third component of a vec3
out_Color = texture2DArray(myTextureSampler, vec3(UV, index)).rgb;
}

[font=arial, verdana, tahoma, sans-serif][size=2]I already made a VertexCoordPointer, it's working great, but if I want to draw tiles with different texture I have to draw one tile at a time or use an atlas texture, is there a limit for texture size?[/font][font=arial, verdana, tahoma, sans-serif][size=2]
[/font][color=#1C2837][size=2]
Jacob Jingle
[size=2][color=#880000]#version 420 core[color=#000000]
uniform sampler2DArray myTextureSampler[color=#666600];[color=#000000]
[color=#000088]in[color=#000000] vec2 UV[color=#666600];[color=#000000]
[color=#000088]in[color=#000000] [color=#000088]int[color=#000000] index[color=#666600];[color=#000000]
[color=#000088]out[color=#000000] vec3 out_Color[color=#666600];[color=#000000]

[color=#000088]void[color=#000000] main[color=#666600]([color=#000088]void[color=#666600])[color=#000000]
[color=#666600]{[color=#000000]
[color=#880000]//Use the texture coordinates as usual but the different textures are indexed by the third component of a vec3[color=#000000]
out_Color [color=#666600]=[color=#000000] texture2DArray[color=#666600]([color=#000000]myTextureSampler[color=#666600],[color=#000000] vec3[color=#666600]([color=#000000]UV[color=#666600],[color=#000000] index[color=#666600])).[color=#000000]rgb[color=#666600];[color=#000000]
[color=#666600]}
[color="#666600"]

[color="#666600"]

[color="#666600"]is that GLSL? if it is i would need to learn about it, since I never used it. But I think I understand your idea, that's very close to what I wanted to use. Thanks.

[font="arial, verdana, tahoma, sans-serif"]I already made a VertexCoordPointer, it's working great, but if I want to draw tiles with different texture I have to draw one tile at a time or use an atlas texture, is there a limit for texture size?[/font]

The code I gave you is one draw call. As for size limit: Texture.

[color="#666600"]is that GLSL? if it is i would need to learn about it, since I never used it. But I think I understand your idea, that's very close to what I wanted to use. Thanks.

Yes this is GLSL(4.20)...And it's definitely worth learning.