渲染时处理多次通过 [英] handle multiple passes when rendering

问题描述

我要渲染一个体积 (VERSION combined with programmable pipeline and fixed pipeline) 仅使用使用glsl的可编程管线(无固定管线).为此，我需要多次通过渲染器，这意味着需要按顺序使用不同的着色器渲染不同的场景. 我想到了three methods

I want to render a volume(VERSION combined with programmable pipeline and fixed pipeline) using only programmable pipeline (no fixed pipeline) which using glsl. To achieve this, I need multipass the renderer which means render different scene with different shaders in a sequential order. There are three methods come to my mind:

1. 使用一个着色器程序并分离着色器->附加着色器->每当渲染新场景时重新编译程序.
2. 每遍使用一个着色器程序，然后退出多个着色器程序.
3. 在渲染不同的遍时使用glsl中的子例程来选择不同的子例程.

我想知道什么时候应该使用第一种方法? 2ed方法?等等.有经验的开发人员可以提供帮助吗?

I wonder when should I use the 1st method? 2ed method? etc. can any experienced developer help?

推荐答案

许多问题无需多次通过即可解决.只是尝试使一种没有它们的技术成为可能. 如果没有其他效果，请使用方法3.

Many problems can be solved without multiple passes. Just try to make a technique without them. If nothing else works use method 3.

我对此的想法:

• 方法1非常慢且无法使用.
• 方法2的工作量很大，但如果 做得好，这是快速".
• 方法3既简单又优雅，但有一个 额外的处理开销.您可以多次渲染对象，然后将当前的通过编号传递给着色器.

• Method 1 is very slow and unuseable.
• Method 2 is much work but if done well it is "fast".
• Method 3 is easy and elegant but has a additional processing overhead. You may render your object several times and pass your current pass number to your shader.

方法3的示例:

uniform int currentPass;

/* OTHER UNIFORMS */

void main()
{
    if(currentPass == 1)
    {
         /* DO SOMETHING */
    }
    else if(currentPass == 2)
    {
         /* DO SOMETHING */
    }
    else if(...) { ... }
}

在我看来，最好的方法是仅使用很少的着色器(也许是一个材质着色器，一个后期处理着色器等)，因此您的方法3几乎是完美的.

On my mind the best approach is to use only very few shaders (maybe one material shader, one post processing shader, etc.), so your method 3 is nearly perfect.

是否曾经考虑过超级着色器?它们就像您的方法3.谷歌" :) 我也建议此问题.

Ever thought about uber-shaders? They are something "like" your method 3. Google it :) I recommend also this question.

也要小心，if语句可能会大大削弱您的性能.

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