#ifdef LOG_DEPTH
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// 1.0 at the near plane, increasing linearly from there.
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varying float v_depthFromNearPlusOne;
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#ifdef SHADOW_MAP
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varying vec3 v_logPositionEC;
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#endif
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#endif
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vec4 czm_updatePositionDepth(vec4 coords) {
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#if defined(LOG_DEPTH)
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#ifdef SHADOW_MAP
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vec3 logPositionEC = (czm_inverseProjection * coords).xyz;
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v_logPositionEC = logPositionEC;
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#endif
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// With the very high far/near ratios used with the logarithmic depth
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// buffer, floating point rounding errors can cause linear depth values
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// to end up on the wrong side of the far plane, even for vertices that
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// are really nowhere near it. Since we always write a correct logarithmic
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// depth value in the fragment shader anyway, we just need to make sure
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// such errors don't cause the primitive to be clipped entirely before
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// we even get to the fragment shader.
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coords.z = clamp(coords.z / coords.w, -1.0, 1.0) * coords.w;
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#endif
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return coords;
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}
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/**
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* Writes the logarithmic depth to gl_Position using the already computed gl_Position.
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*
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* @name czm_vertexLogDepth
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* @glslFunction
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*/
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void czm_vertexLogDepth()
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{
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#ifdef LOG_DEPTH
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v_depthFromNearPlusOne = (gl_Position.w - czm_currentFrustum.x) + 1.0;
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gl_Position = czm_updatePositionDepth(gl_Position);
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#endif
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}
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/**
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* Writes the logarithmic depth to gl_Position using the provided clip coordinates.
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* <p>
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* An example use case for this function would be moving the vertex in window coordinates
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* before converting back to clip coordinates. Use the original vertex clip coordinates.
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* </p>
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* @name czm_vertexLogDepth
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* @glslFunction
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*
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* @param {vec4} clipCoords The vertex in clip coordinates.
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*
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* @example
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* czm_vertexLogDepth(czm_projection * vec4(positionEyeCoordinates, 1.0));
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*/
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void czm_vertexLogDepth(vec4 clipCoords)
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{
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#ifdef LOG_DEPTH
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v_depthFromNearPlusOne = (clipCoords.w - czm_currentFrustum.x) + 1.0;
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czm_updatePositionDepth(clipCoords);
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#endif
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}
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