/**
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* Transforms a position from eye to window coordinates. The transformation
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* from eye to clip coordinates is done using {@link czm_projection}.
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* The transform from normalized device coordinates to window coordinates is
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* done using {@link czm_viewportTransformation}, which assumes a depth range
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* of <code>near = 0</code> and <code>far = 1</code>.
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* <br /><br />
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* This transform is useful when there is a need to manipulate window coordinates
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* in a vertex shader as done by {@link BillboardCollection}.
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*
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* @name czm_eyeToWindowCoordinates
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* @glslFunction
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*
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* @param {vec4} position The position in eye coordinates to transform.
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*
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* @returns {vec4} The transformed position in window coordinates.
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*
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* @see czm_modelToWindowCoordinates
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* @see czm_projection
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* @see czm_viewportTransformation
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* @see BillboardCollection
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*
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* @example
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* vec4 positionWC = czm_eyeToWindowCoordinates(positionEC);
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*/
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vec4 czm_eyeToWindowCoordinates(vec4 positionEC)
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{
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vec4 q = czm_projection * positionEC; // clip coordinates
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q.xyz /= q.w; // normalized device coordinates
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q.xyz = (czm_viewportTransformation * vec4(q.xyz, 1.0)).xyz; // window coordinates
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return q;
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}
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