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5-20.cpp
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5-20.cpp
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#include "OpenGL.h"
#ifdef EX5_20
GLuint program;
GLuint buffer;
int getWindowWidth()
{
return 800;
}
int getWindowHeight()
{
return 600;
}
void onAwake()
{
static const char * vs_source[] =
{
"#version 430 core \n"
" \n"
"layout (binding = 0) uniform area_block \n"
"{ \n"
" uint counter_value; \n"
"}; \n"
" \n"
"out vec4 color; \n"
" \n"
"uniform float max_area; \n"
" \n"
"void main(void) \n"
"{ \n"
" float brightness = clamp(float(counter_value) / max_area, \n"
" 0.0, 1.0); \n"
" color = vec4(brightness, brightness, brightness, 1.0); \n"
"} \n"
};
static const char * fs_source[] =
{
"#version 430 core \n"
" \n"
"layout (binding = 0, offset = 0) uniform atomic_uint area; \n"
" \n"
"void main(void) \n"
"{ \n"
" atomicCounterIncrement(area); \n"
"} \n"
};
program = glCreateProgram();
GLuint fs = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fs, 1, fs_source, NULL);
glCompileShader(fs);
GLuint vs = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vs, 1, vs_source, NULL);
glCompileShader(vs);
CheckShaderCompileError(fs);
CheckShaderCompileError(vs);
glAttachShader(program, vs);
glAttachShader(program, fs);
glLinkProgram(program);
glGenBuffers(1, &buffer);
glBindBuffer(GL_ATOMIC_COUNTER_BUFFER, buffer);
glBufferData(GL_ATOMIC_COUNTER_BUFFER, 16 * sizeof(GLuint), NULL, GL_DYNAMIC_COPY);
glBindBufferBase(GL_ATOMIC_COUNTER_BUFFER, 3, buffer);
const GLuint zero = 0;
glBindBuffer(GL_ATOMIC_COUNTER_BUFFER, buffer);
// Method 1 - Reset atomic counter using glBufferSubData.
glBufferSubData(GL_ATOMIC_COUNTER_BUFFER, 2 * sizeof(GLuint), sizeof(GLuint), &zero);
// Method 2 - Buffer mapping
//GLuint *data = (GLuint *)glMapBufferRange(GL_ATOMIC_COUNTER_BUFFER, 0, 16 * sizeof(GLuint), GL_MAP_WRITE_BIT | GL_MAP_INVALIDATE_RANGE_BIT);
//data[2] = 0;
//glUnmapBuffer(GL_ATOMIC_COUNTER_BUFFER);
// Method 3 - glCelarBufferSubData
//glClearBufferSubData(GL_ATOMIC_COUNTER_BUFFER,
// GL_R32UI,
// 2 * sizeof(GLuint),
// sizeof(GLuint),
// GL_RED_INTEGER, GL_UNSIGNED_INT, &zero);
}
void onUpdate(double current_time)
{
}
void onShutdown()
{
glDeleteProgram(program);
glDeleteBuffers(1, &buffer);
}
#endif