50 lines
1.7 KiB
JavaScript
50 lines
1.7 KiB
JavaScript
import ShaderSource from "../Renderer/ShaderSource.js";
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/**
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* Support for rendering things on only one side of the screen.
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*
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* @private
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*/
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const Splitter = {
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/**
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* Given a fragment shader string, returns a modified version of it that
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* only renders on one side of the screen or the other. Fragments on the
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* other side are discarded. The screen side is given by a uniform called
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* `czm_splitDirection`, which can be added by calling
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* {@link Splitter#addUniforms}, and the split position is given by an
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* automatic uniform called `czm_splitPosition`.
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*/
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modifyFragmentShader: function modifyFragmentShader(shader) {
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shader = ShaderSource.replaceMain(shader, "czm_splitter_main");
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shader +=
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// czm_splitPosition is not declared because it is an automatic uniform.
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"uniform float czm_splitDirection; \n" +
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"void main() \n" +
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"{ \n" +
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// Don't split when rendering the shadow map, because it is rendered from
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// the perspective of a totally different camera.
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"#ifndef SHADOW_MAP\n" +
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" if (czm_splitDirection < 0.0 && gl_FragCoord.x > czm_splitPosition) discard; \n" +
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" if (czm_splitDirection > 0.0 && gl_FragCoord.x < czm_splitPosition) discard; \n" +
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"#endif\n" +
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" czm_splitter_main(); \n" +
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"} \n";
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return shader;
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},
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/**
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* Add `czm_splitDirection` to the given uniform map.
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*
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* @param {object} object The object on which the `splitDirection` property may be found.
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* @param {object} uniformMap The uniform map.
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*/
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addUniforms: function addUniforms(object, uniformMap) {
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uniformMap.czm_splitDirection = function () {
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return object.splitDirection;
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};
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},
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};
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export default Splitter;
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