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60 lines
1.9 KiB
Java
60 lines
1.9 KiB
Java
package com.ctreber.acearth.shader;
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import java.awt.*;
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/**
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* <p>Shader for projections which display the whole surface.</p>
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*
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* <p>© 2002 Christian Treber, ct@ctreber.com (Nov 11, 2002)</p>
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* @author Christian Treber, ct@ctreber.com
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*
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*/
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public class ShaderDefault extends Shader
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{
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public Color[] getShadedColors(int pRowNo, int[] pRowTypes)
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{
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final double y = fProjection.inverseProjectY(fProjection.inverseFinalizeY(pRowNo));
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// conceptually, on each iteration of the i loop, we want:
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//
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// x = Math.sin(INV_XPROJECT(i)) * sqrt(1 - (y*y));
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// z = cos(INV_XPROJECT(i)) * sqrt(1 - (y*y));
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//
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// computing this directly is rather expensive, however, so we only
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// compute the first (i=0) pair of values directly; all other pairs
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// (i>0) are obtained through successive rotations of the original
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// pair (by inv_proj_scale radians).
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//
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// compute initial (x, z) values
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double tmp = Math.sqrt(1 - (y * y));
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double x = Math.sin(fProjection.inverseFinalizeX(0)) * tmp;
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double z = Math.cos(fProjection.inverseFinalizeX(0)) * tmp;
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// compute rotation coefficients used
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// to find subsequent (x, z) values
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tmp = 1 / fProjection.getScale();
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final double sin_theta = Math.sin(tmp);
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final double cos_theta = Math.cos(tmp);
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// save a little computation in the inner loop
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final double lYBySunVectorY = y * fLightVector.getY();
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// use i_lim to encourage compilers to register loop limit
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final Color[] lColors = new Color[pRowTypes.length];
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for(int lColNo = 0; lColNo < pRowTypes.length; lColNo++)
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{
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double lSunValue = (x * fLightVector.getX()) + lYBySunVectorY +
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(z * fLightVector.getZ());
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lColors[lColNo] = getShadedColorForType(pRowTypes[lColNo], lSunValue);
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// compute next (x, z) values via 2-d rotation
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tmp = (cos_theta * z) - (sin_theta * x);
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x = (sin_theta * z) + (cos_theta * x);
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z = tmp;
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}
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return lColors;
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}
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}
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