c - OpenGL 仅在 fb0 中进行第一次纹理渲染

Question

我试图将两个高斯模糊纹理附加到 fbo，以便在着色器中减去它们(在狗中返回 c2-c)，但第一个纹理给出了奇怪的结果。我试图找出问题所在，但我看不出问题出在哪里。如果有人能启发我，我将不胜感激。提前谢谢你。

这是 C 代码:

  static void draw(void) {
  static int b1 = 0;
  static int b2 = 50;

  glBindFramebuffer(GL_FRAMEBUFFER, _fbo);

  blur(_vao, b1, _tId, _fboTex[0], 1, 0);  
  glUseProgram(0);  

  blur(_vao, b2, _tId, _fboTex[0], 1, 1);
  glUseProgram(0);

  glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0);
  glBlitFramebuffer(0, 0, _dim[0], _dim[1], 0, 0, _dim[0], _dim[1], GL_COLOR_BUFFER_BIT, GL_NEAREST);
  //glBlitFramebuffer(0, 0, _dim[0], _dim[1], _dim[0]/2, 0, _dim[0], _dim[1], GL_COLOR_BUFFER_BIT, GL_NEAREST);
  glBindFramebuffer(GL_FRAMEBUFFER, 0);
}

void tex_to_shader(GLuint tid, char * sampler_name, GLuint num_tex){
  glActiveTexture(!num_tex ? GL_TEXTURE0 : GL_TEXTURE1);
  glBindTexture(GL_TEXTURE_2D, 0);  
  glUniform1i(glGetUniformLocation(blurPId, sampler_name), num_tex);
  glBindTexture(GL_TEXTURE_2D, tid);
}

void blur(GLuint plate_vao, GLuint radius, GLuint in, GLuint out, GLuint nb_iterations, GLuint current_texture) {
  int i, n;
  GLuint temp, rin = in;
  glGenTextures(1, &temp);
  glBindTexture(GL_TEXTURE_2D, temp);
  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_REPEAT);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
  glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
  radius = radius > MAX_RADIUS ? MAX_RADIUS : radius;

  for(n = 0; n < (int)nb_iterations; n++) {
    for(i = 0; i < 2; i++) {
      glFramebufferTexture2D(GL_FRAMEBUFFER, !current_texture ? GL_COLOR_ATTACHMENT0 : GL_COLOR_ATTACHMENT1, GL_TEXTURE_2D, i == 0 ? temp : out,  0);
      glUseProgram(blurPId);
      glUniform1i(glGetUniformLocation(blurPId,  "inv"), i ? 1 : 0);
      glUniform1fv(glGetUniformLocation(blurPId, "weight"), MAX_RADIUS, &weights[(radius * (radius - 1)) >> 1]);
      glUniform2fv(glGetUniformLocation(blurPId, "offset"), MAX_RADIUS, (i % 2) ? offsetH : offsetV);
      glUniform1i(glGetUniformLocation(blurPId,  "nweights"), radius);
      glDisable(GL_DEPTH_TEST);
      glBindVertexArray(plate_vao);
      tex_to_shader(rin, !current_texture ? "blur0" : "blur1", current_texture);
      glDrawArrays(GL_TRIANGLE_STRIP, 0, 4); 
      glBindVertexArray(0);
      glBindTexture(GL_TEXTURE_2D, 0);
    }
    rin = out;
  }
    glDeleteTextures(1, &temp);
}

这是我们的片段着色器:

#version 330

uniform sampler2D blur0;
uniform sampler2D blur1;

uniform int current_texture;
uniform int nweights;
uniform float weight[128];
uniform vec2 offset[128];

in  vec2 vsoTexCoord;
out vec4 fragColor;

vec4 dog(sampler2D a, sampler2D b){

    vec4 c  = texture(a, vsoTexCoord.st) * weight[0];
    vec4 c2 = texture(b, vsoTexCoord.st) * weight[0];

    for (int i = 1; i < nweights; i++) {
        c  += texture(a, vsoTexCoord.st + offset[i]) * weight[i];
        c  += texture(a, vsoTexCoord.st - offset[i]) * weight[i];
        c2 += texture(b, vsoTexCoord.st + offset[i]) * weight[i];
        c2 += texture(b, vsoTexCoord.st - offset[i]) * weight[i];
    }
    return c;
}

vec4 gray(vec4 c){
  float moyenne = 0.2126 * c.r + 0.7152 * c.g + 0.0722 * c.b;
  return vec4(moyenne, moyenne, moyenne, 1.0);
}

void main(void) {

  fragColor = dog(blur0,blur1);
  //fragColor = gray(fragColor);
}

Answer 1

如果您使用带有多个颜色附件的帧缓冲区，那么您必须指定应该写入的颜色附件。应该在其中绘制的颜色缓冲区可以由 glDrawBuffers 指定。 .

例如如果只应在 GL_COLOR_ATTACHMENT1 上绘制，则可以这样指定:

GLenum attachment = GL_COLOR_ATTACHMENT1;
glDrawBuffers(1, &attachment); 

在您的情况下，您必须在函数 blur 的开头选择正确的颜色附件:

void blur(GLuint plate_vao, GLuint radius, GLuint in, GLuint out,
    GLuint nb_iterations, GLuint current_texture) {

    GLenum attachment = !current_texture ? GL_COLOR_ATTACHMENT0 : GL_COLOR_ATTACHMENT1;
    glDrawBuffers(1, &attachment);  

    .....
}