glGetUniformLocation 在使用时在转换反馈期间返回 -1

Question

函数returns -1，即使在顶点着色器中定义并使用了Uniform，我怀疑原因可能是输出属性可能没有与目标缓冲区正确绑定（不确定是否就是这样）。没有这件制服，我的大部分价值观都会保持不变。

绘制变换反馈

/*code included in update*/
glUseProgram(feedbackShader->GetProgram());

glEnable(GL_RASTERIZER_DISCARD);
/*end of code included in update*/

glBindBuffer(GL_ARRAY_BUFFER, particleBuffer[isEvenBuffer]);
glBindTransformFeedback(GL_TRANSFORM_FEEDBACK, transformBuffer[!isEvenBuffer]);

glEnableVertexAttribArray(0);
glEnableVertexAttribArray(1);
glEnableVertexAttribArray(2);
glEnableVertexAttribArray(3);
glEnableVertexAttribArray(4);
glEnableVertexAttribArray(5);

glVertexAttribPointer(5, 3, GL_FLOAT, GL_FALSE, sizeof(Particle), 0); //Location
glVertexAttribPointer(4, 3, GL_FLOAT, GL_FALSE, sizeof(Particle), (const GLvoid*)12); //Velocity
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(Particle), (const GLvoid*)24); //InitLocation
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(Particle), (const GLvoid*)36); //InitVelocity
glVertexAttribPointer(3, 1, GL_FLOAT, GL_FALSE, sizeof(Particle), (const GLvoid*)48); //Lifetime
glVertexAttribPointer(2, 1, GL_FLOAT, GL_FALSE, sizeof(Particle), (const GLvoid*)52); //InitLifetime

GLint uniformLocation = glGetUniformLocation(feedbackShader->GetProgram(), "time");

glUniform1f(uniformLocation, msec);

glBeginTransformFeedback(GL_POINTS);

glDrawTransformFeedback(GL_POINTS, transformBuffer[isEvenBuffer]);

glEndTransformFeedback();

glDisableVertexAttribArray(0);
glDisableVertexAttribArray(1);
glDisableVertexAttribArray(2);
glDisableVertexAttribArray(3);
glDisableVertexAttribArray(4);
glDisableVertexAttribArray(5);

顶点着色器

#version 410

in vec3 inLocation;
in vec3 inVelocity;
in vec3 inInitLocation;
in vec3 inInitVelocity;
in float inLifeTime;
in float inInitlifeTime;

out vec3 outLocation;
out vec3 outVelocity;
out vec3 outInitLocation;
out vec3 outInitVelocity;
out float outLifeTime;
out float outInitlifeTime;

uniform float time;

vec3 Gravity = vec3(0.0f,-0.98f,0.0f);
float dampeningFactor = 0.5;

void main()
{

  outLifeTime = inLifeTime - time;

  if(outLifeTime > 0.0f){
    outVelocity = (inVelocity + Gravity * time) * dampeningFactor;
    outLocation = inLocation + inVelocity * time;
  }else{
    outVelocity = inInitVelocity;
    outLocation = inInitLocation;
    outLifeTime = inInitlifeTime;
  }
  outInitVelocity = inInitVelocity;
  outInitLocation = inInitLocation;
  outInitlifeTime = inInitlifeTime;
}

更新你们都要求提供一些额外的信息。

顶点着色器

#version 410

in vec3 inLocation;
in vec3 inVelocity;
in vec3 inInitLocation;
in vec3 inInitVelocity;
in float inLifeTime;
in float inInitlifeTime;

out vec3 outLocation;
out vec3 outVelocity;
out vec3 outInitLocation;
out vec3 outInitVelocity;
out float outLifeTime;
out float outInitlifeTime;

uniform float time;

vec3 Gravity = vec3(0.0f,-0.98f,0.0f);
float dampeningFactor = 0.5;

void main()
{

  outLifeTime = inLifeTime - time;

  if(outLifeTime > 0.0f){
    outVelocity = (inVelocity + Gravity * time) * dampeningFactor;
    outLocation = inLocation + inVelocity * time;
  }else{
    outVelocity = inInitVelocity;
    outLocation = inInitLocation;
    outLifeTime = inInitlifeTime;
  }
  outInitVelocity = inInitVelocity;
  outInitLocation = inInitLocation;
  outInitlifeTime = inInitlifeTime;
}

反馈变化（我很愚蠢，一开始没有这个，尽管我的代码中仍然存在同样的问题）

const GLchar* feedbackVaryings[] = {
    "outLocation",
    "outVelocity",
    "outInitLocation",
    "outInitVelocity",
    "outLifeTime",
    "outInitlifeTime"
};
glTransformFeedbackVaryings(feedbackShader->LinkProgram(), 6, feedbackVaryings, GL_INTERLEAVED_ATTRIBS);

我还在 "Drawing the Transform Feedback section" 中添加了 gluseProgram。

Answer 1

我假设指令

feedbackShader->LinkProgram()

链接程序。但是在链接程序之前必须指定变化的变换反馈变量。

见OpenGL 4.6 API Core Profile Specification; 7.3.1.1 Naming Active Resources; page 104

The order of the active resource list is implementation-dependent for all interfaces except for TRANSFORM_FEEDBACK_VARYING. If variables in the TRANSFORM_FEEDBACK_VARYING interface were specified using the TransformFeedbackVaryings command, the active resource list will be arranged in the variable order specified in the most recent call to TransformFeedbackVaryings before the last call to LinkProgram.

这意味着，首先你必须将编译的顶点着色器对象附加到程序对象(glAttachShader). Then you have to specify the transform feedback varying (glTransformFeedbackVaryings). Finally you have to link the program (glLinkProgram):

GLuint shader_obj;
GLuint program_obj;

.....

glAttachShader(program_obj, shader_obj);

const GLchar* feedbackVaryings[] = {
    "outLocation",
    "outVelocity",
    "outInitLocation",
    "outInitVelocity",
    "outLifeTime",
    "outInitlifeTime"
};
glTransformFeedbackVaryings(program_obj, 6, feedbackVaryings, GL_INTERLEAVED_ATTRIBS);

glLinkProgram(program_obj);

此外，我建议使用 Layout Qualifier 来定义顶点着色器输入变量的属性索引。

例如

layout (location = 0) in vec3 inLocation;
layout (location = 1) in vec3 inVelocity;
layout (location = 2) in vec3 inInitLocation;
layout (location = 3) in vec3 inInitVelocity;
layout (location = 4) in float inLifeTime;
layout (location = 5) in float inInitlifeTime;

作为替代方案，属性索引可以通过 glGetAttribLocation after linking the program or set by glBindAttribLocation 在链接程序之前确定。

glGetUniformLocation 在使用时在转换反馈期间返回 -1

glGetUniformLocation returning -1 during transform feedback when it is used

opengl

glsl

transform-feedback