c – 双抛物面阴影映射

我使用的是OpenGL 4.0,GLSL 4.0,不是GLEW或类似的,不是GLU或类似的,不是GLUT或类似的.也使用OpenCL或CUDA,但它们不涉及这种情况.

我一直试图解决我的问题几周没有成功,现在我希望有双抛物面阴影映射经验的人可以给我建议.让我们直接解决问题并检查一些图片(图片1)：

图1包含一些我需要解释的彩色箭头.红色箭头显示我们应该看到的唯一正确的阴影.其他箭头表示阴影错误：黄色箭头表示由细分引起的斑点,也许是蓝色箭头,但它们的位置在前/后半球的边界上.并且绿色箭头指向不应存在的锯齿图案(我们最近看到的例子中没有).现在重要的是要注意上面的图片是使用以下代码行(代码1)计算的：

"swap.z=-sign(swap.z)*swap.z;n" //mostly right results in the main project,but wrong way

这个代码行位于GLSL着色器程序中,它是我在主项目中尝试没有成功的四个候选者之一,从中拍摄照片.但是,正如我们将看到的,代码4确实在单独的测试程序中工作.代码1实际上是完全错误的DPSM方式,但它是我的主项目获得阴影的唯一方式.接下来我们看相同的场景计算有点不同,但仍然错误的代码行(图片2和代码2)：

"swap.z=sign(swap.z)*swap.z;n" //almost dark picture,wrong way

我们再次看同一个场景,但现在我们使用完全不同的正统代码行(图3和代码3)：

"swap.z=-(teDistance-n)/(f-n);n" //lightning is mainly working but no shadows,should be the right way

最后,我们看一下代码行计算的场景,它在我们最近看到的例子中(几乎)完美地工作(图4和代码4)：

"swap.z=(teDistance-n)/(f-n);n" //almost dark picture,doesn't work in the main project,but works in the test program,right way

如果有人怀疑上面图片中看到的文物是由于“阴影痤疮”现象造成的,那么不,我认为它们不是.以下是通过设置SHADOW_EPSILON = 0.000005f并关闭模糊(图5)故意制作阴影痤疮图案的图片：

在这一点上,我需要说,我在两台独立的Windows 7.1笔记本电脑上运行程序,一台配备nVIDIA GeForce GT 525M,另一台配备AMD Radeon R6.结果是一样的.编译器是Visual Studio 2010.在我看来,这是一个纯粹的OpenGL相关问题.

为了解决这个问题,我写了一个单独的小测试程序,最后得到了阴影贴图.据我所知,测试程序的工作方式与制作图片1-5的程序非常相似,但没有优化,并且许多矩阵乘法已经从主机移动到着色器.测试程序源的相关部分如下.着色器优先：

static const char *vertex1=
"#version 400 coren"

"layout (location=1) in vec3 vertexLocation;n"

"out vec3 vPosition;n"

"void main() {n"
    "vPosition=vertexLocation;n"
"}";




static const char *tessIn1=
"#version 400 coren"

"layout (vertices=3) out;n"

"in vec3 vPosition[];n"
"out vec3 tcPosition[];n"

"void main() {n"
    "tcPosition[gl_InvocationID]=vPosition[gl_InvocationID];n"
    "if (gl_InvocationID==0) {n"

        "gl_TessLevelOuter[0]=max(distance(vPosition[1],vPosition[2]),1.0);n"
        "gl_TessLevelOuter[1]=max(distance(vPosition[2],vPosition[0]),1.0);n"
        "gl_TessLevelOuter[2]=max(distance(vPosition[0],vPosition[1]),1.0);n"
        "gl_TessLevelInner[0]=max(0.33*(gl_TessLevelOuter[0]+gl_TessLevelOuter[1]+gl_TessLevelOuter[2]),1.0);n"

    "}n"
"}";


static const char* tessOut1=
"#version 400 coren"

"layout(triangles,equal_spacing,ccw) in;n"

"uniform mat4 model;n"
"uniform mat4 view;n"
"uniform mat4 lightOrientation;n"

"in vec3 tcPosition[];n"
"out float teDistance;n"
"out float teClip;n"

"const float n=0.5;n"
"const float f=20000.0;n"

"void main() {n"

    "vec3 accum=vec3(0.0);n"
    "accum=accum+gl_TessCoord.x*tcPosition[0];n"
    "accum=accum+gl_TessCoord.y*tcPosition[1];n"
    "accum=accum+gl_TessCoord.z*tcPosition[2];n"

// Transform position to the paraboloid's view space
    "vec4 swap=lightOrientation*model*vec4(accum,1.0);n"

//store the distance and other variables
    "teDistance=abs(swap.z);n"
    "teClip=swap.z;n"

//calculate and set X and Y coordinates
    "swap.xyz=normalize(swap.xyz);n"
    "if (swap.z<=0.0) {n"
        "swap.xy=swap.xy/(1.0-swap.z);n"
    "} else {n"
        "swap.xy=swap.xy/(1.0+swap.z);n"
    "}n"

//calculate and set Z and W coordinates
//  "swap.z=-sign(swap.z)*swap.z;n"  //Wrong way
//  "swap.z=sign(swap.z)*swap.z;n"  //Wrong way
//  "swap.z=-(teDistance-n)/(f-n);n"      //Wrong way
    "swap.z=(teDistance-n)/(f-n);n"      //Right way
    "swap.w=1.0;n"

    "gl_Position=swap;n"
"}";


static const char* geometry1=
"#version 400 coren"

"layout(triangles) in;n"
"layout(triangle_strip,max_vertices=3) out;n"

"in float teDistance[];n"
"in float teClip[];n"
"out float gDistance;n"

"void main() {n"
    "for (int i=0; i<3; i++) {n"
        "gDistance=teDistance[i];n"
        "if (teClip[i]<=0.0) {n"
            "gl_Layer=0;n"
        "} else {n"
            "gl_Layer=1;n"
        "}n"
        "gl_Position=gl_in[i].gl_Position;n"
        "EmitVertex();n"
    "}n"
    "EndPrimitive();n"
"}";


static const char* fragment1=
"#version 400 coren"

"in float gDistance;n"

"out vec2 fragmentVari;n"

"void main() {n"

    "fragmentVari=vec2(gDistance,gDistance*gDistance);n"

"}";


const char *vertex2=
"#version 400 coren"

"layout (location=1) in vec3 vertexPosition;n"
"layout (location=2) in vec2 vertexTexCoord;n"
"layout (location=3) in vec3 vertexNormal;n"

"const float n=0.5;n"
"const float f=20000.0;n"

"uniform vec4 colour;n"
"uniform mat4 model;n"
"uniform mat4 view;n"
"uniform mat4 normal;n"
"uniform mat4 projection;n"
"uniform mat4 lightOrientation;n"

"out vec2 texKoord;n"
"out vec3 pointNormal;n"
"out vec3 point;n"
"out vec4 color;n"
"out vec4 vOriginPoint;n"

"void main() {n"
    "texKoord=vertexTexCoord;n"
    "pointNormal=normalize(vec3(normal*vec4(vertexNormal,1.0)));n"
    "point=vec3(model*vec4(vertexPosition,1.0));n"
    "color=colour;n"
    "vOriginPoint=vec4(vertexPosition,1.0);n"
    "gl_Position=projection*view*model*vec4(vertexPosition,1.0);n"
"}";


const char *fragment2=
"#version 400 coren"

"uniform sampler2DArray tex1;n"

"uniform vec4 colour;n"
"uniform mat4 model;n"
"uniform mat4 view;n"
"uniform mat4 normal;n"
"uniform mat4 projection;n"
"uniform mat4 lightOrientation;n"

"in vec2 texKoord;n"
"in vec3 pointNormal;n"
"in vec3 point;n"
"in vec4 color;n"
"in vec4 vOriginPoint;n"
"out vec4 fragmentColor;n"

"const float SHADOW_EPSILON = 0.05f;n"
"const vec3 Ka=vec3(0.05,0.05,0.05);n"  //Ambient reflectivity
"const vec3 Kd=vec3(1.0,1.0,1.0);n"  //Diffuse reflectivity
"const float At=0.4;n"                 //Light attenuation

"vec3 ads(in vec3 position,in vec3 normal) {n"
    "vec3 l=vec3(lightOrientation*model*vOriginPoint);n"
    "vec3 s=normalize(l - position);n"
    "vec3 intensity=vec3(0.5,0.5,0.5)*10.0;n"
    "float attenuation=1.0/(1.0+At*max(length(l),1.0));n"
    "intensity=intensity*attenuation*Kd*abs(dot(s,normal));n"
    "return intensity;n"
"}n"

"float drawShadow() {n"
    "vec3 texKoord;n"
    "vec4 textureDepth;n"

    "vec4 originPoint=vec4(lightOrientation*model*vOriginPoint);n"
    "float distance=abs(originPoint.z);n"
    "vec3 normalized=normalize(originPoint.xyz);n"

    "if (normalized.z<=0.0) {n"
        "texKoord.xy=normalized.xy/(1.0-normalized.z);n"
        "texKoord.xy=0.5*texKoord.xy+0.5;n"
        "texKoord.z=0.0;n"
        "textureDepth=texture(tex1,texKoord);n"
    "} else {n"
        "texKoord.xy=normalized.xy/(1.0+normalized.z);n"
        "texKoord.xy=0.5*texKoord.xy+0.5;n"
        "texKoord.z=1.0;n"
        "textureDepth=texture(tex1,texKoord);n"
    "}n"

    "if (textureDepth.x+SHADOW_EPSILON>=distance) {n"
        "return 1.0;n"
    "} else {n"
        "return 0.0;n"
    "}n"
"}n"

"void main() {n"
    "vec4 lightning=vec4(Ka,1.0);n"
    "swap2=swap2*drawShadow();n"
    "lightning=lightning+swap2;n"
    "fragmentColor=color*lightning;n"
"}";


const char *vertexLight=
"#version 400 coren"

"layout (location=1) in vec3 vertexPosition;n"

"uniform mat4 view;n"
"uniform mat4 projection;n"
"uniform mat4 lightOrientation;n"

"void main() {n"
    "gl_Position=projection*view*lightOrientation*vec4(vertexPosition,1.0);n"
"}";


const char *fragmentLight=
"#version 400 coren"

"out vec4 fragmentColor;n"

"void main() {n"
    "fragmentColor=vec4(1.0,1.0);n"
"}";

这是显示功能：

void TForm1::display()
{
    GLuint loc1,loc2,loc3,loc4,loc5,loc6;
    float swap[16];
    float normal[16]={0.0,0.0,1.0};

//first we render a shadow map
    {
        glUseProgram(shaderT1);
        glBindFramebuffer(GL_FRAMEBUFFER,frameBuffer[0]);
        glClearColor(20000.0f,0.0f,0.0f);
        glDepthMask(GL_TRUE);
        glDepthRange(0,1);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        glViewport(0,textureDim.x,textureDim.y);
        glPatchParameteri(GL_PATCH_VERTICES,3);
        loc1=glGetUniformLocation(shaderT1,"model");
        loc2=glGetUniformLocation(shaderT1,"lightOrientation");
        loc3=glGetUniformLocation(shaderT1,"view");
        swap[0]=1.0; swap[1]=0.0; swap[2]=0.0; swap[3]=0.0;
        swap[4]=0.0; swap[5]=1.0; swap[6]=0.0; swap[7]=0.0;
        swap[8]=0.0; swap[9]=0.0; swap[10]=1.0; swap[11]=0.0;
        swap[12]=-lightMatrix[12]; swap[13]=-lightMatrix[13]; swap[14]=-lightMatrix[14]; swap[15]=1.0;
        glUniformMatrix4fv(loc1,1,GL_FALSE,triangleMatrix);
        glUniformMatrix4fv(loc2,swap);
        glUniformMatrix4fv(loc3,view);
        glBindVertexArray(VAO[1]);
        glDrawArrays(GL_PATCHES,3);
        glUniformMatrix4fv(loc1,identity);
        glUniformMatrix4fv(loc2,view);
        glBindVertexArray(VAO[0]);
        glDrawArrays(GL_PATCHES,6);
    }

//then we render the world and make use of that rendered shadow map
    {
        glUseProgram(shaderT2);
        glBindFramebuffer(GL_FRAMEBUFFER,0);
        glDepthMask(GL_TRUE);
        glDepthRange(0,1);
        glClearColor(0.0f,1.0f,0.0f);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        glUniform1i(glGetUniformLocation(shaderT2,"tex1"),1);
        glActiveTexture(GL_TEXTURE0+1);
        glBindTexture(GL_TEXTURE_2D_ARRAY,texID[0]);
        glViewport(0,512,512);
        loc1=glGetUniformLocation(shaderT2,"model");
        loc2=glGetUniformLocation(shaderT2,"view");
        loc3=glGetUniformLocation(shaderT2,"normal");
        loc4=glGetUniformLocation(shaderT2,"colour");
        loc5=glGetUniformLocation(shaderT2,"projection");
        loc6=glGetUniformLocation(shaderT2,"lightOrientation");

//render a rectangle where the shadow is drawn onto
        glUniformMatrix4fv(loc1,view);
        matrixMultiply4D(swap,view,identity);
        inverseMatrix4D(swap,swap);
        transpose4D(normal,normal);
        glUniform4fv(loc4,red);
        glUniformMatrix4fv(loc5,projection);
        swap[0]=1.0; swap[1]=0.0; swap[2]=0.0; swap[3]=0.0;
        swap[4]=0.0; swap[5]=1.0; swap[6]=0.0; swap[7]=0.0;
        swap[8]=0.0; swap[9]=0.0; swap[10]=1.0; swap[11]=0.0;
        swap[12]=-lightMatrix[12]; swap[13]=-lightMatrix[13]; swap[14]=-lightMatrix[14]; swap[15]=1.0;
        glUniformMatrix4fv(loc6,swap);
        glBindVertexArray(VAO[0]);
        glDrawArrays(GL_TRIANGLES,6);

//render the triangle which makes a shadow
        glUniformMatrix4fv(loc1,triangleMatrix);
        inverseMatrix4D(swap,swap);
         transpose4D(normal,yellow);
        glUniformMatrix4fv(loc5,swap);
        glBindVertexArray(VAO[1]);
        glDrawArrays(GL_TRIANGLES,3);
    }

//finally render a white triangle which represents a location of the light
    {
        glUseProgram(shaderT3);
        glBindFramebuffer(GL_FRAMEBUFFER,1);
        glViewport(0,512);
        loc1=glGetUniformLocation(shaderT3,"view");
        loc2=glGetUniformLocation(shaderT3,"projection");
        loc3=glGetUniformLocation(shaderT3,"lightOrientation");
        glUniformMatrix4fv(loc1,view);
        glUniformMatrix4fv(loc2,projection);
        glUniformMatrix4fv(loc3,lightMatrix);
        glBindVertexArray(VAO[2]);
         glDrawArrays(GL_TRIANGLES,3);
    }

    glFinish();

//rotate a light on it's orbit
    matrixMultiply4D(lightMatrix,rotationMatrix,lightMatrix);

}

我拍了四部电影代表上面的测试程序和代码行1-4.下面是用代码1完成的电影1：

Movie_1

电影2代码2：

Movie_2

电影3代码3：

Movie_3

电影4代码4：

Movie_4

你可以看到Movie 4是唯一一个阴影贴图工作的地方(两个半球之间的边界区域没有阴影,但我可以忍受.但是,如果有人知道如何修复它,我会很高兴如果你告诉我).但它不适用于主项目！我希望你能给我一些关于可能出错的建议,我应该检查或给你你的双抛物面阴影映射代码样本……