如何使用Alpha渲染纹理? [英] How to render a texture with alpha?

问题描述

如何使用Alpha渲染纹理?

How to render a texture with alpha?

我有一个纹理，需要在不同位置使用不同的alpha值渲染它.有办法吗? (我的纹理是GL_RGBA)

I have a texture, and need to render it with different alpha values at different locations. Any way to do so? (My texture is GL_RGBA)

如果无法即时更改Alpha值，我必须为不同的Alpha级别创建不同的纹理吗?

If not possible to change alpha value on the fly, I have to create different textures for different alpha levels?

推荐答案

您的纹理为GL_RGBA，因此每个纹理像素具有不同的alpha值.

Your texture is GL_RGBA so it has a different alpha value for each texel.

如果要更改用于渲染的alpha值，我可以考虑以下方法:

If you want to change the alpha value used for render, I can think of the following methods:

• 更改纹理的alpha值(不确定是否要说的话).
• 使用glColor4f更改顶点的alpha值.它将乘以纹理值.您可能需要使用glEnable(GL_COLOR_MATERIAL)和/或glColorMaterial().
• 使用顶点着色器更改顶点alpha值.它将乘以纹理值.
• 使用片段着色器动态更改采样的纹理值.
• 使用两个纹理阶段并将其相乘.第二个将具有修改后的alpha值(请参见glActiveTexture()和朋友).
• 使用片段着色器和两个(或更多)纹理阶段.这是最酷的！

• Change the texture alpha values (not sure if you say that you don't want to do that).
• Use glColor4f to change the alpha value of the vertices. It will multiply the texture values. You may need to use glEnable(GL_COLOR_MATERIAL) and/or glColorMaterial().
• Use a vertex shader to change the vertex alpha values. It will multiply the texture values.
• Use a fragment shader to change the sampled texture values on the fly.
• Use two texture stages and multiply them. The second one will have the modified alpha values (see glActiveTexture() and friends).
• Use a fragment shader and two (or more) texture stages. This is the coolest!

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