选择纹理的一部分并绘制GPU

Question

I have a few days looking for how to do this, but I'm stuck, if someone can tell me some resource that can be useful for me, I do what I look for, I do not want to write all the code for my only guide me how to do it, "because I think it is possible "

My intention is to host a texture on the GPU, and take, selections, parts of that texture, passing the size you want to take, and draw in "quad" or "mesh" in libgdx.

I can create a multitexture, using vertex and shader, but not like taking parts of a texture to them in another texture, and change the parts that should be drawn.

But maybe this is not the right way to do what I want.

Below, I show an image to understand me better:

1. is the texture on the GPU, original
2. the image, which would be drawn depending on the coordinates that are passed
3. the result would be shown

Answer 1

If I understood your intent correctly, I think what you want is simply texture coordinate or UV mapping. Assuming you have the texture (1), you would then draw four quads, each of them using different texture coordinates to access the multitexture. For example, looking at the top image of (3),

• the top-left and top-right quads would use texture coordinates from [0.0, 0.0] to [0.5, 0.5] to access the black area,
• the bottom-left quad would use texture coordinates from [0.5, 0.5] to [1.0, 1.0] to access the red area, and
• the bottom-right quad would use texture coordinates from [0.5, 0.0] to [1.0, 0.5] to access the blue area.

If you want, you can create a function that maps the "atlas frame index" 1, 2, 3 or 4 to the correct texture coordinates to make drawing easier.