由三角形条组成的四边形上的OpenGL ES 1.1中纹理变形的问题 [英] Problems with texture deformation in OpenGL ES 1.1 on quad made out of triangle strips

问题描述

我正在使用三角带创建一个四边形.问题是当我尝试使用要在形状上均匀插值的矩形纹理进行绘制时.

I'm using triangle strips to create a quad. The problem is when I try to paint it using a rectangular texture that I want to have evenly interpolated over the shape.

只要形状是矩形或矩形的仿射变换，我将拥有两个相同的三角形来构建形状，一切都会顺利进行.但是，对于任意形状，三角形具有不同的形状，并且沿三角形的公共边缘自然会发生变形.

As long as the shape is a rectangle or an affine transform of a rectangle, I'll have two identical triangles that build the shape and everything goes well. But with arbitrary shapes, the triangles have different shapes and a distortion naturally occurs along the common edge of the triangles.

   _____       ______       _____
  |     |     /     /       \   /
  |_____|    /_____/         \_/

    Ok         Ok           Not Ok

我想在ES 2.0中使用自定义着色器解决此问题将非常简单，但是如何在ES 1.1中实现呢?

I imagine it would be fairly straightforward to work around this with custom shaders in ES 2.0, but how do I achieve it in ES 1.1?

推荐答案

直截了当，如果您不提供纹理坐标的深度/深度信息，则硬件只能对纹理坐标进行线性插值.

Put bluntly, the hardware can only do linear interpolation of texture coordinates if you don't provide it with perspective/depth information.

线性插值不能正确处理导致问题的情况.

Linear interpolation does not allow to properly handle the case that causes you problems.

要在边缘上进行适当的插值，必须在四边形中引入透视信息.

To have a proper interpolation on you edge, you have to introduce perspective information in your quad.

您应该在此NVidia白皮书中找到更多信息:投影纹理映射.

You should find more information in this NVidia whitepaper : Projective Texture Mapping.

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