Question

本教程后我使用ARB扩展实现了阴影贴图 http://www.paulsprojects.net/tutorials/smt/smt.html 我修改了代码以添加另一个光源。我创建并初始化了另外两个矩阵（lightViewMatrix2和lightProjectionMatrix2）以及另一个shadowMap纹理。在本教程的第3步，绑定第一个阴影贴图纹理后，我将第二个阴影贴图绑定。我得到的结果是我只看到2个不同光源产生的2个阴影之间的交叉点。我已经初始化了init函数中的所有矩阵，如教程中所示，这是我的显示函数。

void Display(void){
//First pass - from light's point of view
//Calculate & save matrices LIGHT 1
glPushMatrix();
    glLoadIdentity();
    gluLookAt(  lightPosition[0], lightPosition[1], lightPosition[2],
                0.0f, 0.0f , 0.0f,
                0.0f, 1.0f, 0.0f);
    glGetFloatv(GL_MODELVIEW_MATRIX, lightViewMatrix);
glPopMatrix();

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

glMatrixMode(GL_PROJECTION);
glLoadMatrixf(lightProjectionMatrix);

glMatrixMode(GL_MODELVIEW);
glLoadMatrixf(lightViewMatrix);

//Use viewport the same size as the shadow map
glViewport(0, 0, shadowMapSize, shadowMapSize);

//Draw back faces into the shadow map
glCullFace(GL_FRONT);

//Disable color writes, and use flat shading for speed
glShadeModel(GL_FLAT);
glColorMask(0, 0, 0, 0);

//Draw the scene
DrawScene();

//Read the depth buffer into the shadow map texture
glBindTexture(GL_TEXTURE_2D, shadowMapTexture[0]);
glCopyTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 0, 0, shadowMapSize, shadowMapSize);


//First pass - from light's point of view
//Calculate & save matrices LIGHT 2
glPushMatrix();
    glLoadIdentity();
    gluLookAt(  lightPosition2[0], lightPosition2[1], lightPosition2[2],
                0.0f, 0.0f , 0.0f,
                0.0f, 1.0f, 0.0f);
    glGetFloatv(GL_MODELVIEW_MATRIX, lightViewMatrix2);
glPopMatrix();

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

glMatrixMode(GL_PROJECTION);
glLoadMatrixf(lightProjectionMatrix2);

glMatrixMode(GL_MODELVIEW);
glLoadMatrixf(lightViewMatrix2);

//Use viewport the same size as the shadow map
glViewport(0, 0, shadowMapSize, shadowMapSize);

//Draw the scene
DrawScene();

//Read the depth buffer into the shadow map texture
glBindTexture(GL_TEXTURE_2D, shadowMapTexture[1]);
glCopyTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 0, 0, shadowMapSize, shadowMapSize);

//restore states
glCullFace(GL_BACK);
glShadeModel(GL_SMOOTH);
glColorMask(1, 1, 1, 1);


//2nd pass - Draw from camera's point of view
glClear(GL_DEPTH_BUFFER_BIT);

glMatrixMode(GL_PROJECTION);
glLoadMatrixf(cameraProjectionMatrix);

glMatrixMode(GL_MODELVIEW);
glLoadMatrixf(cameraViewMatrix);

glViewport(0, 0, windowWidth, windowHeight);

float white2[3]={0.2f,0.2f,0.2f};

//light to represent shadowed areas
glLightfv(GL_LIGHT1, GL_POSITION, VECTOR4D(lightPosition));
glLightfv(GL_LIGHT1, GL_AMBIENT, white2);
glLightfv(GL_LIGHT1, GL_DIFFUSE, white2);
glLightfv(GL_LIGHT1, GL_SPECULAR, black1);
glEnable(GL_LIGHT1);
glEnable(GL_LIGHTING);

DrawScene();


//3rd pass
//Draw with bright light LIGHT1
glLightfv(GL_LIGHT1, GL_DIFFUSE, white1);
glLightfv(GL_LIGHT1, GL_SPECULAR, white1);

//Calculate texture matrix for projection
//This matrix takes us from eye space to the light's clip space
//It is postmultiplied by the inverse of the current view matrix when specifying texgen
static MATRIX4X4 biasMatrix(0.5f, 0.0f, 0.0f, 0.0f,
                            0.0f, 0.5f, 0.0f, 0.0f,
                            0.0f, 0.0f, 0.5f, 0.0f,
                            0.5f, 0.5f, 0.5f, 1.0f);    //bias from [-1, 1] to [0, 1]

MATRIX4X4 textureMatrix=biasMatrix*lightProjectionMatrix*lightViewMatrix;

//Set up texture coordinate generation.
glTexGeni(GL_S, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR);
glTexGenfv(GL_S, GL_EYE_PLANE, textureMatrix.GetRow(0));
glEnable(GL_TEXTURE_GEN_S);

glTexGeni(GL_T, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR);
glTexGenfv(GL_T, GL_EYE_PLANE, textureMatrix.GetRow(1));
glEnable(GL_TEXTURE_GEN_T);

glTexGeni(GL_R, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR);
glTexGenfv(GL_R, GL_EYE_PLANE, textureMatrix.GetRow(2));
glEnable(GL_TEXTURE_GEN_R);

glTexGeni(GL_Q, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR);
glTexGenfv(GL_Q, GL_EYE_PLANE, textureMatrix.GetRow(3));
glEnable(GL_TEXTURE_GEN_Q);

//Bind & enable shadow map texture
glBindTexture(GL_TEXTURE_2D, shadowMapTexture[0]);
glEnable(GL_TEXTURE_2D);

//Enable shadow comparison
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_MODE_ARB, GL_COMPARE_R_TO_TEXTURE);

//Shadow comparison should be true (ie not in shadow) if r<=texture
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_FUNC_ARB, GL_LEQUAL);

//Shadow comparison should generate an INTENSITY result
glTexParameteri(GL_TEXTURE_2D, GL_DEPTH_TEXTURE_MODE_ARB, GL_INTENSITY);

//Set alpha test to discard false comparisons
glAlphaFunc(GL_GEQUAL, 0.99f);
glEnable(GL_ALPHA_TEST);

DrawScene();

//3rd pass
//Draw with bright light LIGHT2

MATRIX4X4 textureMatrix2=biasMatrix*lightProjectionMatrix2*lightViewMatrix2;

//Set up texture coordinate generation.
glTexGeni(GL_S, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR);
glTexGenfv(GL_S, GL_EYE_PLANE, textureMatrix2.GetRow(0));
glEnable(GL_TEXTURE_GEN_S);

glTexGeni(GL_T, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR);
glTexGenfv(GL_T, GL_EYE_PLANE, textureMatrix2.GetRow(1));
glEnable(GL_TEXTURE_GEN_T);

glTexGeni(GL_R, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR);
glTexGenfv(GL_R, GL_EYE_PLANE, textureMatrix2.GetRow(2));
glEnable(GL_TEXTURE_GEN_R);

glTexGeni(GL_Q, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR);
glTexGenfv(GL_Q, GL_EYE_PLANE, textureMatrix2.GetRow(3));
glEnable(GL_TEXTURE_GEN_Q);

//Bind & enable shadow map texture
glBindTexture(GL_TEXTURE_2D, shadowMapTexture[1]);
glEnable(GL_TEXTURE_2D);

//Enable shadow comparison
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_MODE_ARB, GL_COMPARE_R_TO_TEXTURE);

//Shadow comparison should be true (ie not in shadow) if r<=texture
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_FUNC_ARB, GL_LEQUAL);

//Shadow comparison should generate an INTENSITY result
glTexParameteri(GL_TEXTURE_2D, GL_DEPTH_TEXTURE_MODE_ARB, GL_INTENSITY);

//Set alpha test to discard false comparisons
glAlphaFunc(GL_GEQUAL, 0.99f);
glEnable(GL_ALPHA_TEST);

DrawScene();

//Disable textures and texgen
glDisable(GL_TEXTURE_2D);

glDisable(GL_TEXTURE_GEN_S);
glDisable(GL_TEXTURE_GEN_T);
glDisable(GL_TEXTURE_GEN_R);
glDisable(GL_TEXTURE_GEN_Q);

//Restore other states
glDisable(GL_LIGHTING);
glDisable(GL_ALPHA_TEST);


//Set matrices for ortho
glMatrixMode(GL_PROJECTION);
glPushMatrix();
glLoadIdentity();
gluOrtho2D(-1.0f, 1.0f, -1.0f, 1.0f);

glMatrixMode(GL_MODELVIEW);
glPushMatrix();
glLoadIdentity();

//reset matrices
glMatrixMode(GL_PROJECTION);
glPopMatrix();
glMatrixMode(GL_MODELVIEW);
glPopMatrix();

glFinish();
glutSwapBuffers();}

Answer 1

你在这里做的是你首先为第一盏灯生成阴影贴图，然后在为第二盏灯生成阴影贴图的同时与第一张阴影贴图进行比较。结果你最终得到的影子是两者的某种组合。您需要以与生成第一个阴影相同的方式生成第二个阴影（每个灯光的阴影生成应该独立于其他每个灯光）然后最后因为您需要使用一些多纹理以某种方式执行相同的比较检查每个z纹理独立。

考虑使用基于着色器的方法，因为所有这些固定函数调用都已过时，并且没有着色器优势。我读到的关于使用许多灯光进行阴影贴图的最佳文章是“大量的具有分层渲染的阴影投射灯”作者：DanielRákos。它提供了一种非常有效的方法。

具有多个阴影的阴影映射

1 个答案: