如何制作阴影贴图？

Question

我试图了解 Shadow Mapping 是如何独立工作的，并描述了这个 Python 程序来测试 Shadow Mapping，这是尽可能的。

我搜索了阴影贴图问题，但我还没有找到类似这样的问题，那么我该如何给光前的普通旋转立方体上色以及如何校正阴影，使其出现并将其准确放置在表面上？我只是在修改着色器。

import pyglet, math, pyrr, ctypes
import numpy as np
from OpenGL.GL import *
from OpenGL.GL.shaders import *

app = pyglet.window.Window()

v = """
in layout(location=0) vec3 posicao;
uniform mat4 view;
uniform vec3 translate;
uniform float rot;
uniform float rot2;
uniform vec3 t2;
out vec3 outpos;
void main(){
    vec3 p = posicao;
    p = vec3(sin(rot)*p.x+cos(rot)*p.z,p.y,-sin(rot)*p.z+cos(rot)*p.x);
    p = translate+p+t2;
    p = vec3(p.x,sin(rot2)*p.z+cos(rot2)*p.y,-sin(rot2)*p.y+cos(rot2)*p.z);
    outpos = p;
    gl_Position = view*vec4(p,1);
}
"""

f = """
uniform vec3 cor;
uniform int modo;
uniform sampler2D shadow;
in vec3 outpos;
void main(){
    if(modo==0){
        float pi = 3.141592653589793;
        vec3 o = outpos+vec3(0,-5,0);
        o = vec3(o.x,sin(-30*pi/180)*o.z+cos(-30*pi/180)*o.y,-sin(-30*pi/180)*o.y+cos(-30*pi/180)*o.z);
        o.z+=0.05;
        float d = texture(shadow,vec2(.5)+o.xy/20).z;
        float i = 1;
        if(d<-o.z/20){
            i = 0.5;
        }
        gl_FragColor = vec4(vec3(cor),1)*i;
        //gl_FragColor = texture(shadow,outpos.xy);
    }else{
        gl_FragColor = vec4(vec3(-outpos.z/20),1);
    }
}
"""

shader = compileProgram(compileShader(v,GL_VERTEX_SHADER),compileShader(f,GL_FRAGMENT_SHADER))

glUseProgram(shader)

tudo = [-200,-4,200,
        200,-4,200,
        200,-4,-200,
        -200,-4,-200,
        -2,-2,2,
        -2,-2,-2,
        2,-2,-2,
        2,-2,2,
        2,2,2,
        2,2,-2,
        -2,2,-2,
        -2,2,2,
        -2,2,2,
        -2,2,-2,
        -2,-2,-2,
        -2,-2,2,
        2,-2,2,
        2,-2,-2,
        2,2,-2,
        2,2,2,
        -2,2,-2,
        2,2,-2,
        2,-2,-2,
        -2,-2,-2,
        -2,-2,2,
        2,-2,2,
        2,2,2,
        -2,2,2]

tudo = np.array(tudo, dtype=np.float32)

CUBO = glGenBuffers(1)

glBindBuffer(GL_ARRAY_BUFFER, CUBO)
glBufferData(GL_ARRAY_BUFFER, len(tudo)*4, tudo, GL_STREAM_DRAW)

glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 12, ctypes.c_void_p(0))
glEnableVertexAttribArray(0)

view = pyrr.matrix44.create_perspective_projection_matrix(60, app.width/app.height, .1, 10000)
p = glGetUniformLocation(shader, "view")
glUniformMatrix4fv(p, 1, GL_FALSE, view)

glEnable(GL_DEPTH_TEST)

# Tentativa de Shadow Mapping

glEnable(GL_TEXTURE_2D)

tf = glGenTextures(1)
glBindTexture(GL_TEXTURE_2D, tf)
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, app.width, app.height, 0, GL_RGB, GL_UNSIGNED_BYTE, None)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR)
f = glGenFramebuffers(1)
r = glGenRenderbuffers(1)
glBindFramebuffer(GL_FRAMEBUFFER, f)
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, tf, 0)
glBindRenderbuffer(GL_RENDERBUFFER, r)
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8, app.width, app.height)
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, r)
glBindRenderbuffer(GL_RENDERBUFFER, 0)
glBindFramebuffer(GL_FRAMEBUFFER, 0)

pos = [0,-10,0]
comando = {"a":0,"w":0,"s":0,"d":0,"q":0,"e":0}
girar = -1

@app.event
def on_draw():
    global CUBO, shader, pos, comando, tudo, girar, f
    glBindFramebuffer(GL_FRAMEBUFFER, f)
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
    # Z-Buffer
    p = glGetUniformLocation(shader, "modo")
    glUniform1i(p, 1)
    p = glGetUniformLocation(shader, "rot2")
    glUniform1f(p, -30*math.pi/180)
    p = glGetUniformLocation(shader, "t2")
    glUniform3f(p, 0, -5, 0)
    # Movimento
    v = .04
    if comando["a"] == 1:
        pos[0]-=v
    if comando["d"] == 1:
        pos[0]+=v
    if comando["w"] == 1:
        pos[1]-=v
    if comando["s"] == 1:
        pos[1]+=v
    if comando["q"] == 1:
        pos[2]-=v
    if comando["e"] == 1:
        pos[2]+=v
    # fundo vermelho
    p = glGetUniformLocation(shader, "translate")
    glUniform3f(p, 0, 0, 0)
    p = glGetUniformLocation(shader, "rot")
    glUniform1f(p, 0)
    p = glGetUniformLocation(shader, "cor")
    glUniform3f(p, 1, 0, 0)
    glDrawArrays(GL_QUADS, 0, 4)
    # objeto no meio
    p = glGetUniformLocation(shader, "translate")
    glUniform3f(p, -1, -5, -10)
    p = glGetUniformLocation(shader, "rot")
    glUniform1f(p, 0)
    p = glGetUniformLocation(shader, "cor")
    glUniform3f(p, 0, 0, 1)
    glDrawArrays(GL_QUADS, 8, 4)
    # objeto azul
    p = glGetUniformLocation(shader, "translate")
    glUniform3f(p, pos[0], pos[2], pos[1])
    p = glGetUniformLocation(shader, "rot")
    girar+=.4
    glUniform1f(p, girar*math.pi/180)
    p = glGetUniformLocation(shader, "cor")
    glUniform3f(p, 0, 0, 1)
    glDrawArrays(GL_QUADS, 4, 8)
    p = glGetUniformLocation(shader, "cor")
    glUniform3f(p, 0, 1, 0)
    glDrawArrays(GL_QUADS, 12, 8)
    p = glGetUniformLocation(shader, "cor")
    glUniform3f(p, 1, 1, 0)
    glDrawArrays(GL_QUADS, 20, 8)
    # gravar o Framebuffer
    glBindFramebuffer(GL_FRAMEBUFFER, 0)
    # reset
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
    # Z-Buffer tirando
    p = glGetUniformLocation(shader, "modo")
    glUniform1i(p, 0)
    p = glGetUniformLocation(shader, "rot2")
    glUniform1f(p, 0*math.pi/180)
    p = glGetUniformLocation(shader, "t2")
    glUniform3f(p, 0, 0, 0)
    # fundo vermelho
    p = glGetUniformLocation(shader, "translate")
    glUniform3f(p, 0, 0, 0)
    p = glGetUniformLocation(shader, "rot")
    glUniform1f(p, 0)
    p = glGetUniformLocation(shader, "cor")
    glUniform3f(p, 1, 0, 0)
    glDrawArrays(GL_QUADS, 0, 4)
    # objeto no meio
    p = glGetUniformLocation(shader, "translate")
    glUniform3f(p, -1, -5, -10)
    p = glGetUniformLocation(shader, "rot")
    glUniform1f(p, 0)
    p = glGetUniformLocation(shader, "cor")
    glUniform3f(p, 0, 0, 1)
    glDrawArrays(GL_QUADS, 8, 4)
    # objeto azul
    p = glGetUniformLocation(shader, "translate")
    glUniform3f(p, pos[0], pos[2], pos[1])
    p = glGetUniformLocation(shader, "rot")
    glUniform1f(p, girar*math.pi/180)
    p = glGetUniformLocation(shader, "cor")
    glUniform3f(p, 0, 0, 1)
    glDrawArrays(GL_QUADS, 4, 8)
    p = glGetUniformLocation(shader, "cor")
    glUniform3f(p, 0, 1, 0)
    glDrawArrays(GL_QUADS, 12, 8)
    p = glGetUniformLocation(shader, "cor")
    glUniform3f(p, 1, 1, 0)
    glDrawArrays(GL_QUADS, 20, 8)

@app.event
def on_key_press(k,m):
    global comando, grandeG
    if k == pyglet.window.key.A:
        comando["a"] = 1
    if k == pyglet.window.key.W:
        comando["w"] = 1
    if k == pyglet.window.key.S:
        comando["s"] = 1
    if k == pyglet.window.key.D:
        comando["d"] = 1
    if k == pyglet.window.key.Q:
        comando["q"] = 1
    if k == pyglet.window.key.E:
        comando["e"] = 1

@app.event
def on_key_release(k,m):
    global comando
    if k == pyglet.window.key.A:
        comando["a"] = 0
    if k == pyglet.window.key.W:
        comando["w"] = 0
    if k == pyglet.window.key.S:
        comando["s"] = 0
    if k == pyglet.window.key.D:
        comando["d"] = 0
    if k == pyglet.window.key.Q:
        comando["q"] = 0
    if k == pyglet.window.key.E:
        comando["e"] = 0

def SRO(dt):
    on_draw()

pyglet.clock.schedule(SRO)

pyglet.app.run()

Answer 1

问题是由阴影深度缓冲区的精度有限引起的。由于每个片段只有 1 个通道需要存储在阴影缓冲区中，我建议使用浮点内部纹理格式 GL_R16F（或 GL_R32F）：

glTexImage2D(GL_TEXTURE_2D, 0, GL_R16F, app.width, app.height, 0, GL_RED, GL_UNSIGNED_BYTE, None)

注意（阴影）深度现在存储在红色通道中，因此您必须从红色 (x) 通道而不是蓝色 (z) 通道读取值在片段着色器中：

~~floaz d = texture(shadow,vec2(.5)+o.xy/20).z;~~

float d = texture(shadow,vec2(.5)+o.xy/20).x;

如何制作阴影贴图？

How to make Shadow Mapping?

python

opengl

pyglet

glsl

shadow-mapping