怎么样`glTexEnv`，`glColor4x`和`在OpenGL ES 1.0的相关glBlendFunc`？ [英] How are `glTexEnv`, `glColor4x` and `glBlendFunc` related in OpenGL ES 1.0?

问题描述

我看着SurfaceFlinger的，即在code，它是在做组成Android和我听不太懂一些的OpenGL ES 1.0的调用如我只编ES 2.0 code。

I'm looking at SurfaceFlinger, i.e. the the code that is doing the composition in Android, and I have trouble understanding some of the OpenGL ES 1.0 calls as I've only programmed ES 2.0 code.

下面那张件code的我感兴趣的：

Here goes the piece of code that interests me:

glTexEnvx(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
glColor4x(0x10000, 0x10000, 0x10000, 0x10000);
glEnable(GL_BLEND);
glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);

什么是应该做的是混合纹理到缓冲区中。

What it is supposed to be doing is blending a texture into the buffer.

为什么人需要 glTextEnvx 和 glColor4x 电话？是不是 glBlendFunc 够实现混合？

Why does one need the glTextEnvx and glColor4x calls? Isn't glBlendFunc enough for achieving blending?

我的知道的我的问题很幼稚，但我还是不明白什么是 glTexEnvx ，即使读的文档。

I know my question is naive, but I still don't understand what is glTexEnvx for even after reading the docs.

推荐答案

glTexEnv（）设置纹理环境模式。 GL_REPLACE 告诉渲染器跳过当前颜色（例如，从 glColor4（）），而是告诉渲染器使用纹理的颜色为每个对应的像素。如果是你，而不是 GL_REPLACE 中，使用 GL_MODULATE ，那么你的 glColor4（）的通话将被包含在纹理的颜色放在一起时，渲染器设置一个像素的颜色。

glTexEnv() sets the texture environment mode. GL_REPLACE tells the renderer to skip the current color (for example, from glColor4()) and instead tells the renderer to use your texture's colors for every corresponding pixel. If you, instead of GL_REPLACE, use GL_MODULATE, then your glColor4() call will be included together with the texture's colors when the renderer sets a pixel's color.

您 glColor4（）通话不应该做任何事情（当使用 GL_REPLACE ），可以看到上你的对象。

Your glColor4() call shouldn't be doing anything (when using GL_REPLACE) that can be seen on your object.

关于您的 glBlendFunc（）参数：

GL_ONE 当前使用的颜色来自传入原始的，我们称之为源的。 GL_ONE_MINUS_SRC_ALPHA 是相乘的目标的（这是在帧缓存当前存储像素）由（​​1 - 源Alpha值）

GL_ONE is using the current color that comes from your incoming primitive, which we call source. GL_ONE_MINUS_SRC_ALPHA is multiplying the destination (which is the currently stored pixel in the frame buffer) by (1 - source alpha value).

通常情况下，当你不使用纹理，你实现了从的颜色的原语的透明效果时， glColor4（）包含一个alpha值其中1等于完全不透明和0完全透明。

Normally, when you're not using textures, you achieve a transparent effect from color primitives when the glColor4() contains an alpha value where 1 equals fully opaque and 0 fully transparent.

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