绘制许多纹理化的小队OpenGL ES 2.0

Question

I'm programming an Android App where a grid is drawn, which you can move around and move in it's direction. The grid consists of about 2000 to 5000 quads, each with a different texture. I defined 4 vertices and use an index buffer to draw each quad. Before drawing I position it using a model matrix. As you can move in my scene I use view frustum culling, which increases the performance in some situations. Unfortunately there might be the case where I will need to draw all of the quads, so I want to ask how I prevent slow drawing.

I can't use a texture atlas as all of the textures are pretty big (from 256x256 to 1024x1024). I think calling glDrawElements() for each squad is what makes me slow, but I don't know how I can change it.

Another idea I had would be to draw the scene to a texture and just bind this texture to a single quad to create an illusion of the scene being drawn. As the user gets closer I could redraw it for better resolution. Could this work?

I look forward for any kind of help.

Answer 1

I can't use a texture atlas as all of the textures are pretty big (from 256x256 to 1024x1024).

You can fit 64 256x256 textures into a 2048x2048 atlas, that's a huge amount, so you should definitely atlas. Even getting 4 1024x1024 onto a 2048x2048 is worth doing, it can quarter your draw call count.

And as WLGfx says in the comments to your question, you should batch up any quads that use the same texture (with atlasing there will be a lot more of these).

I think this would be enough, but you still might have a pretty high drawcall count in your fully zoomed-out view. After implementing atlasing and batching, if performance here is still a problem, you could create a separate asset set of thumb-nail textures at, say, quarter resolution (so a 256x256 becomes 64x64). This thumbnail asset set would fit onto just a handful of 2048x2048 atlas sheets, and you could switch to it when zoomed out far enough.

Another idea I had would be to draw the scene to a texture and just bind this texture to a single quad to create an illusion of the scene being drawn. As the user gets closer I could redraw it for better resolution. Could this work?

This could work, as long as your scene is very static, if the quads are moving/changing every frame, then it might not help. Also, there might be a noticeable framerate hitch when you have to do the full redraw.