由于某些原因,我正在努力将ZUI从SVG移植到WebGL,并且我想使用片段着色器渲染网格。
以下是我https://dl.dropboxusercontent.com/u/412963/steel/restel_2.mp4
的基本效果我想要一个每10个单位有一条细线, 1px 线的三角形,每100个单位有一条更粗的 2px 线(这里的单位是任意但与世界空间一致,而不是屏幕空间。)
这是我迄今为止所拥有的,没有视频中的次要粗线(请注意,这实际上是我的开放缓冲区的副本,显然不是正确的):
顶点着色器:
attribute vec3 aVertexPosition;
uniform mat4 uMVMatrix;
uniform mat4 uPMatrix;
varying float vX;
varying float vY;
void main(void) {
vX = aVertexPosition.x;
vY = aVertexPosition.y;
gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0);
}
Fragment Shader:
precision mediump float;
uniform vec2 resolution;
uniform float uZoomFactor;
varying float vX;
varying float vY;
void main(void) {
float distance = gl_FragCoord.z / gl_FragCoord.w;
float fuzz = 1.0 / distance;
float minorLineFreq;
if (distance > 10.0) {
minorLineFreq = 1.0;
} else if (distance > 5.0) {
minorLineFreq = 1.0;
} else {
minorLineFreq = 0.10;
}
float xd = mod(vX, minorLineFreq) * 88.1;
float yd = mod(vY, minorLineFreq) * 88.1;
if (xd < fuzz) {
gl_FragColor = vec4(0.0,0.0,0.0,1.0);
} else if (yd < fuzz) {
gl_FragColor = vec4(0.0,0.0,0.0,1.0);
} else {
gl_FragColor = vec4(1.0, 1.0, 1.0, 1.0);
}
}
它在一定距离处产生近似正确的图像(但请注意带有2px线而不是1px的条带效果):
带有条带的网格 使用不需要的粗线放大网格
那么,如何在WebGL片段着色器内部获得一致的网格,每个距离都有1px粗线?
答案 0 :(得分:5)
我相信我找到了一个可以接受的解决方案。
使用以下顶点(以三角形条绘制):
[ 1.0 1.0 0.0
-1.0 1.0 0.0
1.0 -1.0 0.0
-1.0 -1.0 0.0]
顶点着色器:
attribute vec4 aVertexPosition;
void main(void) {
gl_Position = aVertexPosition;
}
Fragment Shader:
precision mediump float;
uniform float vpw; // Width, in pixels
uniform float vph; // Height, in pixels
uniform vec2 offset; // e.g. [-0.023500000000000434 0.9794000000000017], currently the same as the x/y offset in the mvMatrix
uniform vec2 pitch; // e.g. [50 50]
void main() {
float lX = gl_FragCoord.x / vpw;
float lY = gl_FragCoord.y / vph;
float scaleFactor = 10000.0;
float offX = (scaleFactor * offset[0]) + gl_FragCoord.x;
float offY = (scaleFactor * offset[1]) + (1.0 - gl_FragCoord.y);
if (int(mod(offX, pitch[0])) == 0 ||
int(mod(offY, pitch[1])) == 0) {
gl_FragColor = vec4(0.0, 0.0, 0.0, 0.5);
} else {
gl_FragColor = vec4(1.0, 1.0, 1.0, 1.0);
}
}
给出结果(取决于音高和偏移量),如: