Question

我尝试构建一个OpenGL程序，该程序同时对五个值执行牛顿-拉夫森方法。实际上，我只是想学习如何使用TRANSFORM FEEDBACK

顶点着色器只是将值传递给几何着色器

const GLchar* vertexShaderSrc = R"glsl(
#version 330 core

layout (location = 0) in float result;
layout (location = 1) in float val;
layout (location = 2) in float iterTime;
layout (location = 3) in float type;

out float geoResult;
out float geoVal;
out float geoIterTime;
out float geoType;

void main()
{
    geoResult = result;
    geoVal =  val;
    geoIterTime = iterTime;
    geoType = type;
})glsl";

“几何着色器”会在第一次创建五个新值以通过变换反馈进行缓冲和缓存。然后，程序对五个值进行迭代。

const GLchar* geometryShaderSrc = R"glsl(
#version 330 core
layout(points) in;
layout(points,max_vertices=100) out;

#define START_POINT 1.0f
#define REST_POINT 2.0f

in float geoResult[];
in float geoVal[];
in float geoIterTime[];
in float geoType[];

out float outResult;
out float outVal;
out float outIterTime;
out float outType;

void main(){
    if(geoType[0] == START_POINT){
        for(int i = 1; i<=5; ++i){
            outResult = geoVal[0]/2;
            outVal = geoVal[0]+50*i;
            outIterTime = geoIterTime[0];
            outType = REST_POINT;
            EmitVertex();
        }
        EndPrimitive();
    }
    else{
        outResult = geoResult[0]/2 +  geoVal[0] / geoResult[0]/2;
        outVal = geoVal[0];
        outIterTime = geoIterTime[0] - 1;
        outType = REST_POINT;
        EmitVertex();
        EndPrimitive();
    }
} )glsl";

循环如下

while (iterTimeCount-->0)
{

    glEnable(GL_RASTERIZER_DISCARD);
    // specify VBO and TFO
    glBindBuffer(GL_ARRAY_BUFFER, nodeBuffer[currVB]);
    glBindTransformFeedback(GL_TRANSFORM_FEEDBACK, transformFeedback[currTFB]);



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


    glVertexAttribPointer(0, 1, GL_FLOAT, GL_FALSE, sizeof(resolveNode), (const GLvoid*) 0);  // result
    glVertexAttribPointer(1, 1, GL_FLOAT, GL_FALSE, sizeof(resolveNode), (const GLvoid*) 4);  // val
    glVertexAttribPointer(2, 1, GL_FLOAT, GL_FALSE, sizeof(resolveNode), (const GLvoid*) 8);  // iterTime
    glVertexAttribPointer(3, 1, GL_FLOAT, GL_FALSE, sizeof(resolveNode), (const GLvoid*) 12); // type

    glBeginTransformFeedback(GL_POINTS);

    // specially do drawing for the first particle. the rest of the particles will be
    // create and drawn by TransformFeedback
    if (isFirst) {
        glDrawArrays(GL_POINTS, 0, 1);

        isFirst = false;
    }
    else {
        glDrawTransformFeedback(GL_POINTS, transformFeedback[currVB]);
    }

    glEndTransformFeedback();

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

    glGetBufferSubData(GL_TRANSFORM_FEEDBACK_BUFFER,
                       0, sizeof(feedback), feedback);

    for(int i = 0; i < 5; ++i){
        printf("%f\t%f\t%f\t| ",feedback[i].result,feedback[i].val,feedback[i].iterTime);
    }

    printf("\n\n");


    // switch VBO and TBO
    currVB = currTFB;
    currTFB = (currTFB + 1) & 0x1;
}

专注于 feedback [i] .iterTime ，我得到10 10 8 8 8 6 6 4 4 2 2 0，应该是10 9 8 7 6 5 4 3 2 1 0。 ..

glGetBufferSubData在两次glDrawTransformFeedback（）迭代之间返回相同的数据

0 个答案: