在创建着色器方面我完全是个菜鸟。或者更好地说,我昨天才知道。
我正在尝试创建一个非常简单的圆圈。我以为我终于明白了,但事实证明它太大了。它应该与应用滤镜的 DisplayObject 大小相匹配。
片段着色器:
precision mediump float;
varying vec2 vTextureCoord;
vec2 resolution = vec2(1.0, 1.0);
void main() {
vec2 uv = vTextureCoord.xy / resolution.xy;
uv -= 0.5;
uv.x *= resolution.x / resolution.y;
float r = 0.5;
float d = length(uv);
float c = smoothstep(d,d+0.003,r);
gl_FragColor = vec4(vec3(c,0.5,0.0),1.0);
}
使用 Pixi.js 的示例:
var app = new PIXI.Application();
document.body.appendChild(app.view);
var background = PIXI.Sprite.fromImage("required/assets/bkg-grass.jpg");
background.width = 200;
background.height = 200;
app.stage.addChild(background);
var vertexShader = `
attribute vec2 aVertexPosition;
attribute vec2 aTextureCoord;
uniform mat3 projectionMatrix;
varying vec2 vTextureCoord;
void main(void)
{
gl_Position = vec4((projectionMatrix * vec3(aVertexPosition, 1.0)).xy, 0.0, 1.0);
vTextureCoord = aTextureCoord;
}
`;
var fragShader = `
precision mediump float;
varying vec2 vTextureCoord;
vec2 resolution = vec2(1.0, 1.0);
void main() {
vec2 uv = vTextureCoord.xy / resolution.xy;
uv -= 0.5;
uv.x *= resolution.x / resolution.y;
float r = 0.5;
float d = length(uv);
float c = smoothstep(d,d+0.003,r);
gl_FragColor = vec4(vec3(c,0.5,0.),1.0);
}
`;
var filter = new PIXI.Filter(vertexShader, fragShader);
filter.padding = 0;
background.filters = [filter];
body { margin: 0; }
<script src="https://cdnjs.cloudflare.com/ajax/libs/pixi.js/4.5.2/pixi.js"></script>
Pixi.js 的
vTextureCoord
不会从 0 到 1。
来自文档
V4 滤波器与 V3 不同。您不能只添加着色器并假设纹理坐标在 [0,1] 范围内。
...
注意:vTextureCoord 乘以filterArea.xy 就是边界框的实际大小。
如果要获取像素坐标,请使用统一的filterArea,它会自动传递给过滤器。
uniform vec4 filterArea; ... vec2 pixelCoord = vTextureCoord * filterArea.xy;
它们以像素为单位。如果我们想要“将椭圆填充到边界框中”之类的东西,那么这是行不通的。那么,让我们也传递维度吧! PIXI 不会自动执行此操作,我们需要手动修复:
filter.apply = function(filterManager, input, output) { this.uniforms.dimensions[0] = input.sourceFrame.width this.uniforms.dimensions[1] = input.sourceFrame.height // draw the filter... filterManager.applyFilter(this, input, output); }
让我们在着色器中组合它!
uniform vec4 filterArea; uniform vec2 dimensions; ... vec2 pixelCoord = vTextureCoord * filterArea.xy; vec2 normalizedCoord = pixelCoord / dimensions;
这是您更新的代码片段。
var app = new PIXI.Application();
document.body.appendChild(app.view);
var background = PIXI.Sprite.fromImage("required/assets/bkg-grass.jpg");
background.width = 200;
background.height = 200;
app.stage.addChild(background);
var vertexShader = `
attribute vec2 aVertexPosition;
attribute vec2 aTextureCoord;
uniform mat3 projectionMatrix;
varying vec2 vTextureCoord;
void main(void)
{
gl_Position = vec4((projectionMatrix * vec3(aVertexPosition, 1.0)).xy, 0.0, 1.0);
vTextureCoord = aTextureCoord;
}
`;
var fragShader = `
precision mediump float;
varying vec2 vTextureCoord;
uniform vec2 dimensions;
uniform vec4 filterArea;
void main() {
vec2 pixelCoord = vTextureCoord * filterArea.xy;
vec2 uv = pixelCoord / dimensions;
uv -= 0.5;
float r = 0.5;
float d = length(uv);
float c = smoothstep(d,d+0.003,r);
gl_FragColor = vec4(vec3(c,0.5,0.),1.0);
}
`;
var filter = new PIXI.Filter(vertexShader, fragShader);
filter.apply = function(filterManager, input, output)
{
this.uniforms.dimensions[0] = input.sourceFrame.width
this.uniforms.dimensions[1] = input.sourceFrame.height
// draw the filter...
filterManager.applyFilter(this, input, output);
}
filter.padding = 0;
background.filters = [filter];
body { margin: 0; }
<script src="https://cdnjs.cloudflare.com/ajax/libs/pixi.js/4.5.2/pixi.js"></script>