我正在尝试改进Joost van Dongen的内部映射着色器，并尝试实现自阴影。但我还没弄清楚投射阴影光矢量所需的坐标。你可以在这里看到效果有点好的演示。
为了观察情况我将光位置与摄像机位置相比加了一个偏移量，但显然这样看起来也不对。
着色器代码如下。在片段着色器中查找 SHADOWS DEV。涉及的向量是：shad_E和shad_I。
顶点着色器：
varying vec3 oP; // surface position in object space
varying vec3 oE; // position of the eye in object space
varying vec3 oI; // incident ray direction in object space
varying vec3 shad_E; // shadow light position
varying vec3 shad_I; // shadow direction
uniform vec3 lightPosition;
void main() {
// inverse veiw matrix
mat4 modelViewMatrixInverse = InverseMatrix( modelViewMatrix );
// surface position in object space
oP = position;
// position of the eye in object space
oE = modelViewMatrixInverse[3].xyz;
// incident ray direction in object space
oI = oP - oE;
// link the light position to camera for testing
// need to find a way for world space directional light to work
shad_E = oE - lightPosition;
// light vector
shad_I = oP - shad_E;
gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );
}
片元着色器：
varying vec3 oP; // surface position in object space
varying vec3 oE; // position of the eye in object space
varying vec3 oI; // incident ray direction in object space
varying vec3 shad_E; // shadow light position
varying vec3 shad_I; // shadow direction
uniform vec3 wallFreq;
uniform float wallsBias;
uniform vec3 wallCeilingColor;
uniform vec3 wallFloorColor;
uniform vec3 wallXYColor;
uniform vec3 wallZYColor;
float checker(vec2 uv, float checkSize) {
float fmodResult = mod( floor(checkSize * uv.x) + floor(checkSize * uv.y), 2.0);
if (fmodResult < 1.0) {
return 1.0;
} else {
return 0.85;
}
}
void main() {
// INTERIOR MAPPING by Joost van Dongen
// http://interiormapping.oogst3d.net/
// email: joost@ronimo-games.com
// Twitter: @JoostDevBlog
vec3 wallFrequencies = wallFreq / 2.0 - wallsBias;
//calculate wall locations
vec3 walls = ( floor( oP * wallFrequencies) + step( vec3( 0.0 ), oI )) / wallFrequencies;
//how much of the ray is needed to get from the oE to each of the walls
vec3 rayFractions = ( walls - oE) / oI;
//texture-coordinates of intersections
vec2 intersectionXY = (oE + rayFractions.z * oI).xy;
vec2 intersectionXZ = (oE + rayFractions.y * oI).xz;
vec2 intersectionZY = (oE + rayFractions.x * oI).zy;
//use the intersection as the texture coordinates for the ceiling
vec3 ceilingColour = wallCeilingColor * checker( intersectionXZ, 2.0 );
vec3 floorColour = wallFloorColor * checker( intersectionXZ, 2.0 );
vec3 verticalColour = mix(floorColour, ceilingColour, step(0.0, oI.y));
vec3 wallXYColour = wallXYColor * checker( intersectionXY, 2.0 );
vec3 wallZYColour = wallZYColor * checker( intersectionZY, 2.0 );
// SHADOWS DEV // SHADOWS DEV // SHADOWS DEV // SHADOWS DEV //
vec3 shad_P = oP; // just surface position in object space
vec3 shad_walls = ( floor( shad_P * wallFrequencies) + step( vec3( 0.0 ), shad_I )) / wallFrequencies;
vec3 shad_rayFr = ( shad_walls - shad_E ) / shad_I;
// Cast shadow from ceiling planes (intersectionXZ)
wallZYColour *= mix( 0.3, 1.0, step( shad_rayFr.x, shad_rayFr.y ));
verticalColour *= mix( 0.3, 1.0, step( rayFractions.y, shad_rayFr.y ));
wallXYColour *= mix( 0.3, 1.0, step( shad_rayFr.z, shad_rayFr.y ));
// SHADOWS DEV // SHADOWS DEV // SHADOWS DEV // SHADOWS DEV //
// intersect walls
float xVSz = step(rayFractions.x, rayFractions.z);
vec3 interiorColour = mix(wallXYColour, wallZYColour, xVSz);
float rayFraction_xVSz = mix(rayFractions.z, rayFractions.x, xVSz);
float xzVSy = step(rayFraction_xVSz, rayFractions.y);
interiorColour = mix(verticalColour, interiorColour, xzVSy);
gl_FragColor.xyz = interiorColour;
}