Throws:

• DeveloperError : options.textureScale must be greater than 0.0 and less than or equal to 1.0.
• DeveloperError : options.pixelFormat must be a color format.
• DeveloperError : When options.pixelDatatype is FLOAT, this WebGL implementation must support floating point textures. Check context.floatingPointTexture.

Examples:

// Simple stage to change the color
const fs =`
    uniform sampler2D colorTexture;
    in vec2 v_textureCoordinates;
    uniform float scale;
    uniform vec3 offset;
    void main() {
        vec4 color = texture(colorTexture, v_textureCoordinates);
        out_FragColor = vec4(color.rgb * scale + offset, 1.0);
    }`;
scene.postProcessStages.add(new Cesium.PostProcessStage({
    fragmentShader : fs,
    uniforms : {
        scale : 1.1,
        offset : function() {
            return new Cesium.Cartesian3(0.1, 0.2, 0.3);
        }
    }
}));

// Simple stage to change the color of what is selected.
// If czm_selected returns true, the current fragment belongs to geometry in the selected array.
const fs =`
    uniform sampler2D colorTexture;
    in vec2 v_textureCoordinates;
    uniform vec4 highlight;
    void main() {
        vec4 color = texture(colorTexture, v_textureCoordinates);
        if (czm_selected()) {
            vec3 highlighted = highlight.a * highlight.rgb + (1.0 - highlight.a) * color.rgb;
            out_FragColor = vec4(highlighted, 1.0);
        } else {
            out_FragColor = color;
        }
    }`;
const stage = scene.postProcessStages.add(new Cesium.PostProcessStage({
    fragmentShader : fs,
    uniforms : {
        highlight : function() {
            return new Cesium.Color(1.0, 0.0, 0.0, 0.5);
        }
    }
}));
stage.selected = [cesium3DTileFeature];

See:

• PostProcessStageComposite