# 回复：\[cesium-dev\] Re: how transport a picture to postProcessStage
**URL:** https://community.cesium.com/t/cesium-dev-re-how-transport-a-picture-to-postprocessstage/7803
**Category:** CesiumJS
**Created:** [December 14, 2018, 4:27pm UTC](https://community.cesium.com/t/cesium-dev-re-how-transport-a-picture-to-postprocessstage/7803 "2018-12-14T16:27:08Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@noble](https://community.cesium.com/u/noble)
#### Post date: [December 14, 2018, 4:27pm UTC](https://community.cesium.com/t/cesium-dev-re-how-transport-a-picture-to-postprocessstage/7803/1 "2018-12-14T16:27:08Z")
do i need bind texture created by webgl to a textureUint? what’ the max number of textureUnit used by cesium?
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### Author:  [@omar](https://community.cesium.com/u/omar)
#### Post date: [December 17, 2018, 6:25pm UTC](https://community.cesium.com/t/cesium-dev-re-how-transport-a-picture-to-postprocessstage/7803/2 "2018-12-17T18:25:28Z")
It’s hard to tell here without seeing your full code. Have you already successfully rendered the scene to a texture? Can you show the code for that?
> By the way ,are gl\_FragCoord.z and gl\_FragCoord.w in postProcessStage the same as raw WebGL ?
It should be, yes.
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### Author:  [@noble](https://community.cesium.com/u/noble)
#### Post date: [December 18, 2018, 4:06pm UTC](https://community.cesium.com/t/cesium-dev-re-how-transport-a-picture-to-postprocessstage/7803/3 "2018-12-18T16:06:05Z")
a lot of errors from consolo,like below
WebGL: INVALID\_ENUM: bindTexture: invalid target
[.WebGL-11FFF320]RENDER WARNING: there is no texture bound to the unit 0
and it seems render to srceen when I use ”viewer.scene.render()“ after “gl.bindFramebuffer(gl.FRAMEBUFFER, fbo)”
these are my code ,but it seems not work properly.
//store current camera status
var curCameraPos = viewer.scene.camera.positionWC;
var curCameraDir = viewer.scene.camera.direction;
var curCameraUp = viewer.scene.camera.up;
//camera go to light postion
viewer.scene.camera.position = visibleStartPoint;
viewer.scene.camera.direction = new Cesium.Cartesian3(endPoint.x - visibleStartPoint.x, endPoint.y - visibleStartPoint.y, endPoint.z - visibleStartPoint.z)
//record lightView Matrix;
var lightViewMatrix = viewer.scene.camera.viewMatrix;
// Get the rendering context for WebGL
var gl = viewer.canvas.getContext(“webgl”)
> > viewer.canvas.getContext(“experimental-webgl”);
var OFFSCREEN\_WIDTH = 2048, OFFSCREEN\_HEIGHT = 2048;
gl.activeTexture(gl.TEXTURE0);
//create frameBufferObject
var fbo = initFramebufferObject(gl, OFFSCREEN\_WIDTH,OFFSCREEN\_HEIGHT);
gl.bindFramebuffer(gl.FRAMEBUFFER, fbo); // Change the drawing destination to FBO
gl.viewport(0, 0, OFFSCREEN\_HEIGHT, OFFSCREEN\_HEIGHT); // Set view port for FBO
gl.clear(gl.COLOR\_BUFFER\_BIT | gl.DEPTH\_BUFFER\_BIT); // Clear FBO
//render to fbo
viewer.scene.render();
// Change the drawing destination to color buffer
gl.bindFramebuffer(gl.FRAMEBUFFER, null);
gl.viewport(0, 0, viewer.canvas.width, viewer.canvas.height);
gl.clear(gl.COLOR\_BUFFER\_BIT | gl.DEPTH\_BUFFER\_BIT); // Clear
//restore camera postion
viewer.scene.camera.position = curCameraPos;
viewer.scene.camera.direction = curCameraDir;
viewer.scene.render();//
//then I add texture of fbo to postProcessStage
viewer.scene.postProcessStages.add(new Cesium.PostProcessStage({
fragmentShader: FSHADER\_SOURCE,
uniforms: {
u\_ShadowMap: fbo.texture}
});
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### Author:  [@omar](https://community.cesium.com/u/omar)
#### Post date: [December 18, 2018, 9:58pm UTC](https://community.cesium.com/t/cesium-dev-re-how-transport-a-picture-to-postprocessstage/7803/4 "2018-12-18T21:58:32Z")
I think you might need to dig around in the source to see some examples of this. I think you need to initialize a Texture object:
[https://github.com/AnalyticalGraphicsInc/cesium/blob/master/Source/Renderer/Texture.js](https://github.com/AnalyticalGraphicsInc/cesium/blob/master/Source/Renderer/Texture.js)
Or possible just use the createUniform function to wrap it:
[https://github.com/AnalyticalGraphicsInc/cesium/blob/master/Source/Renderer/createUniform.js](https://github.com/AnalyticalGraphicsInc/cesium/blob/master/Source/Renderer/createUniform.js)
You might also find this series helpful for context in understanding Cesium’s rendering engine and where to look in the source code:
> **[Graphics Tech in Cesium - Renderer Architecture | cesium.com](https://cesium.com/blog/2015/05/15/graphics-tech-in-cesium-architecture/)**
>
> Cesium is built on a custom WebGL engine - the Renderer - that we started developing in March 2011 when the WebGL 1.0 spec was released. I consider this a 4...
And more blogs on that:
[https://cesium.com/blog/categories/webgl/](https://cesium.com/blog/categories/webgl/)
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### Author:  [@noble](https://community.cesium.com/u/noble)
#### Post date: [June 14, 2019, 6:24am UTC](https://community.cesium.com/t/cesium-dev-re-how-transport-a-picture-to-postprocessstage/7803/5 "2019-06-14T06:24:51Z")
## Is there some example code for rendering to FBO, I am still blocked here
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### Author:  [@omar](https://community.cesium.com/u/omar)
#### Post date: [June 20, 2019, 9:49pm UTC](https://community.cesium.com/t/cesium-dev-re-how-transport-a-picture-to-postprocessstage/7803/6 "2019-06-20T21:49:00Z")
I think Rayman’s blog post here talks a bit about it, and there’s a link to his app’s source code that might be helpful:
[https://cesium.com/blog/2019/04/29/gpu-powered-wind/](https://cesium.com/blog/2019/04/29/gpu-powered-wind/)