openGLES 2-有没有一种方法可以在不扩展为无符号字节的情况下，每1位加载一个带有alpha元素的纹理？

Question

I have a bitmask that I would like to set as a texture to play with (eg sample from it setting alpha to either 0 or 1, or use it as stencil test).

Do I need to make each bit in this existing mask into a byte and use GL_UNSIGNED_BYTE or is there a more clever way to use this mask?

Answer 1

OpenGLES 2 has only one texture format with single bit alpha: GL_UNSIGNED_SHORT_5_5_5_1 , a 16-bit RGBA texture. If you have any use of the 15-bits of RGB, I'd say it is your best shot. Using compressed texture may or may not work better.

For single bit stencil there is the GL_OES_STENCIL1 extension, however it is really simple using a single bit plane in an 8-bit stencil (in fact very few use more than a single bit plane at a time).

Using stencil requries you to create, render and project into a RenderBuffer, and then render that RenderBuffer onto the next target (eg default framebuffer).

Not sure about your use case, but I cannot think of any where this would be worth the effort compared to just roll with 8-bit alpha set to [0.0,1.0] through and through. If you are after performance, stick to mainstream solutions and let the driver work its magic.