OpenGL场景渲染为黑色与阴影映射

我正在尝试在我的OpenGL引擎中使用本教程实现阴影映射:http://www.fabiensanglard.net/shadowmapping/index.php

我没有任何问题，而制作阴影地图(我认为)。但是使用它，场景完全是阴影。

我渲染场景的方式如下:

• 设置深度FBO

  GLuint sdepthtex;
  GLuint sframebuffer ;
  glGenTextures(1, &sdepthtex);
  glBindTexture(GL_TEXTURE_2D, sdepthtex);
  glTexImage2D(GL_TEXTURE_2D, 0,GL_DEPTH_COMPONENT16, 1024, 1024, 0,GL_DEPTH_COMPONENT, GL_FLOAT, 0);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_FUNC, GL_LEQUAL);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_MODE, GL_COMPARE_R_TO_TEXTURE);
  glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, sdepthtex, 0);
  glDrawBuffer(GL_NONE);
  glReadBuffer(GL_NONE);
  if(glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
  {
   displayMessage("Error loading the Depth Framebuffer");
   return;
  }
  

  
  
  
  

• 从光的角度制作ModelViewProjection矩阵，并将其存储在shadowMatrix变量中。

我使用的函数:

Matrix getMVPmatrix(vector3 position,vector3 lookat )
{
 glPushMatrix();
 double projection[16];
 double modelView[16];
 SDL_Surface*screen = SDL_GetVideoSurface();
 glMatrixMode(GL_PROJECTION);
 glLoadIdentity();
 gluPerspective(FOVY,screen->w/screen->h,NEAR,FAR);
 glMatrixMode(GL_MODELVIEW);
 glEnable(GL_DEPTH_TEST);
 glLoadIdentity();
 gluLookAt(position.x,position.y,position.z,lookat.x,lookat.y,lookat.z,0,1,0);
 glGetDoublev(GL_MODELVIEW_MATRIX, modelView);
 glGetDoublev(GL_PROJECTION_MATRIX, projection);
 Matrix m1(projection);
 Matrix m2(modelView);
 glPopMatrix();
 return m1*m2;
}

• 在depth framebuffer中渲染场景。着色器:

顶点着色器:

uniform mat4 shadowMatrix;
void main()
{
    gl_Position = shadowMatrix*gl_Vertex;  
} 

片段着色器:

void main(void)
{
    gl_FragDepth = gl_FragCoord.z;
}

对于我的3个盒子场景，线性化的深度看起来像这样:

http://www.2shared.com/photo/IExy9aUo/Depth.html

所以我认为shadowMatrix和深度渲染是正确的。

• 最后一关就是用阴影贴图绘制场景

顶点着色器:

varying vec4 ShadowCoord;
uniform mat4 shadowMatrix;
mat4 biasMatrix = mat4(
0.5, 0.0, 0.0, 0.0,
0.0, 0.5, 0.0, 0.0,
0.0, 0.0, 0.5, 0.0,
0.5, 0.5, 0.5, 1.0
);
void main (void)
{
    gl_TexCoord[0] =  gl_MultiTexCoord0;
    gl_FrontColor = gl_Color;
    gl_Position = ftransform();
    ShadowCoord = biasMatrix*shadowMatrix *vec4(gl_Vertex.xyz,1.0);
}

片段着色器:

uniform sampler2D tex;
uniform sampler2D shadowtex;//the non linearized depth texture we made in the 3rd step.
varying vec4 ShadowCoord;
float getShadowFactor(void)
{
    vec4 shadowCoordinateWdivide = ShadowCoord / ShadowCoord.w ;
    shadowCoordinateWdivide.z += 0.0005;
    float distanceFromLight = texture2D(shadowtex,shadowCoordinateWdivide.st).z;
    float shadow = 1.0;
    if (ShadowCoord.w > 0.0)
        shadow = distanceFromLight < shadowCoordinateWdivide.z ? 0.5 :1.0 ;
    return shadow ;
}
void main (void)
{
    gl_FragColor =texture2D(tex, gl_TexCoord[0].st);
    gl_FragColor.rgb *= getShadowFactor() ;//add shadows Here
}

结果呢?我所有的场景都被阴影了!

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_FUNC, GL_LEQUAL);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_MODE, GL_COMPARE_R_TO_TEXTURE);

uniform sampler2D shadowtex;

uniform sampler2DShadow shadowtex;