这是我正在尝试的一段代码：
#include <unistd.h>
#include "GL/gl3w.h"
#include "GLFW/glfw3.h"
#include <math.h>
#include <stdio.h>
#include <string.h>
class application {
private:
static void APIENTRY debug_callback(GLenum source,
GLenum type,
GLuint id,
GLenum severity,
GLsizei length,
const GLchar* message,
GLvoid* userParam);
public:
application() {}
virtual ~application() {}
// virtual void run(application* the_app)
void run()
{
bool running = true;
// app = the_app;
if (!glfwInit())
{
fprintf(stderr, "Failed to initialize GLFW\n");
return;
}
init();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, info.majorVersion);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, info.minorVersion);
if (info.flags.robust)
{
glfwWindowHint(GLFW_CONTEXT_ROBUSTNESS, GLFW_LOSE_CONTEXT_ON_RESET);
}
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
glfwWindowHint(GLFW_SAMPLES, info.samples);
glfwWindowHint(GLFW_STEREO, info.flags.stereo ? GL_TRUE : GL_FALSE);
{
window = glfwCreateWindow(info.windowWidth, info.windowHeight, info.title, info.flags.fullscreen ? glfwGetPrimaryMonitor() : NULL, NULL);
if (!window)
{
fprintf(stderr, "Failed to open window\n");
return;
}
}
glfwMakeContextCurrent(window);
gl3wInit();
startup();
do
{
render(glfwGetTime());
glfwSwapBuffers(window);
glfwPollEvents();
running &= (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_RELEASE);
running &= (glfwWindowShouldClose(window) != GL_TRUE);
} while (running);
shutdown();
glfwDestroyWindow(window);
glfwTerminate();
}
virtual void init()
{
strcpy(info.title, "OpenGL SuperBible Example");
info.windowWidth = 800;
info.windowHeight = 600;
info.majorVersion = 4;
info.minorVersion = 5;
info.samples = 0;
info.flags.all = 0;
info.flags.cursor = 1;
}
virtual void startup() { }
virtual void render(double currentTime) { }
virtual void shutdown() { }
void setWindowTitle(const char * title) { glfwSetWindowTitle(window, title); }
virtual void onResize(int w, int h)
{
info.windowWidth = w;
info.windowHeight = h;
}
void getMousePosition(int& x, int& y)
{
double dx, dy;
glfwGetCursorPos(window, &dx, &dy);
x = static_cast<int>(floor(dx));
y = static_cast<int>(floor(dy));
}
public:
struct APPINFO
{
char title[128];
int windowWidth;
int windowHeight;
int majorVersion;
int minorVersion;
int samples;
union
{
struct
{
unsigned int fullscreen : 1;
unsigned int vsync : 1;
unsigned int cursor : 1;
unsigned int stereo : 1;
unsigned int debug : 1;
unsigned int robust : 1;
};
unsigned int all;
} flags;
};
protected:
APPINFO info;
static application * app;
GLFWwindow* window;
};
class tessellatedtri_app : public application
{
void init()
{
static const char title[] = "OpenGL SuperBible - Tessellated Triangle";
application::init();
memcpy(info.title, title, sizeof(title));
}
virtual void startup()
{
static const char * vs_source[] =
{
"#version 450 core \n"
"layout (location = 0) in vec4 offset; \n"
"layout (location = 1) in vec4 color; \n"
"out vec4 vs_color; \n"
"void main(void) \n"
"{ \n"
" const vec4 vertices[] = vec4[](vec4( 0.25, -0.25, 0.5, 1.0), \n"
" vec4(-0.25, -0.25, 0.5, 1.0), \n"
" vec4( 0.25, 0.25, 0.5, 1.0)); \n"
" \n"
" gl_Position = vertices[gl_VertexID] + offset; \n"
" vs_color = color; \n"
"} \n"
};
static const char * tcs_source[] =
{
"#version 450 core \n"
"layout (vertices = 3) out; \n"
" in vec4 vs_colors [];\n"
" out vec4 tcs_colors [3];\n"
"patch out vec4 patch_color; \n"
"void main(void) \n"
"{ \n"
// gl_TessLevelInner and gl_TessLevelOuter should only be set once
" if (gl_InvocationID == 0) \n"
" { \n"
" gl_TessLevelInner[0] = 3.0; \n"
" gl_TessLevelOuter[0] = 2.0; \n"
" gl_TessLevelOuter[1] = 2.0; \n"
" gl_TessLevelOuter[2] = 2.0; \n"
" } \n"
// " patch_color = vec4(.2, .3, .8); \n"
// " patch_color = vs_colors [gl_InvocationID]; \n"
// " tcs_colors[gl_InvocationID] = vs_colors[gl_InvocationID]; \n"
" gl_out[gl_InvocationID].gl_Position = gl_in[gl_InvocationID].gl_Position; \n"
"} \n"
};
static const char * tes_source[] =
{
"#version 450 core \n"
"layout (triangles, equal_spacing, cw) in; \n"
// "patch in vec4 patch_color; \n"
// " out vec4 tes_color; \n"
"void main(void) \n"
"{ \n"
" gl_Position = (gl_TessCoord.x * gl_in[0].gl_Position) + \n"
" (gl_TessCoord.y * gl_in[1].gl_Position) + \n"
" (gl_TessCoord.z * gl_in[2].gl_Position); \n"
// " tes_color = patch_color; \n"
"} \n"
};
static const char * fs_source[] =
{
"#version 450 core \n"
"in vec4 tes_color; \n"
"out vec4 color; \n"
"void main(void) \n"
"{ \n"
" color = vec4(0.2, 0.2, .4, 1.0); \n"
// " color = tes_color;"
"} \n"
};
program = glCreateProgram();
GLuint vs = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vs, 1, vs_source, NULL);
glCompileShader(vs);
GLuint tcs = glCreateShader(GL_TESS_CONTROL_SHADER);
glShaderSource(tcs, 1, tcs_source, NULL);
glCompileShader(tcs);
GLuint tes = glCreateShader(GL_TESS_EVALUATION_SHADER);
glShaderSource(tes, 1, tes_source, NULL);
glCompileShader(tes);
GLuint fs = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fs, 1, fs_source, NULL);
glCompileShader(fs);
glAttachShader(program, vs);
glAttachShader(program, tcs);
glAttachShader(program, tes);
glAttachShader(program, fs);
glLinkProgram(program);
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);
glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
}
virtual void render(double currentTime)
{
float color_var = ((float)sin(currentTime) + 1.f) / 2.f;
bg_color[0] = color_var;
glClearBufferfv(GL_COLOR, 0, bg_color);
glUseProgram(program);
float offset[] = {
(float) sin(currentTime) * .5f,
(float) cos(currentTime) * .5f,
(float) cos(currentTime) * .5f,
0.0f
};
glVertexAttrib4fv(0, offset);
fg_color[2] = color_var;
glVertexAttrib4fv(1, fg_color);
glDrawArrays(GL_PATCHES, 0, 3);
}
virtual void shutdown()
{
glDeleteVertexArrays(1, &vao);
glDeleteProgram(program);
}
private:
float bg_color[3] = {1.f, .7f, .8f};
float fg_color[3] = {.2f, .7f, .2f};
GLuint program;
GLuint vao;
};
int main(int argc, const char ** argv)
{
tessellatedtri_app *app = new tessellatedtri_app();
app->run();
delete app;
return 0;
}
我只是试图按时间改变线框的颜色，但是经过多次尝试后，我不知为何无法通过阶段传递color属性。有什么建议么？谢谢。
答案 0 :(得分：1)
您需要在任何阶段都要传递的属性的输入和输出：
顶点着色器：
layout (location = 1) in vec4 color;
out vec4 vs_color;
void main(void)
{
vs_color = color;
// ...
}
在Tessellation Control Shader中，属性可以通过以下方式传递：
in vec4 vs_color[];
out vec4 tcs_colors[];
void main(void)
{
tcs_colors[gl_InvocationID] = vs_color[gl_InvocationID];
// ...
}
在Tessellation Evaluation Shader中，您必须根据每个顶点输入来计算“镶嵌”属性：
in vec4 tcs_colors[];
out vec4 tes_colors;
void main(void)
{
tes_colors = gl_TessCoord.x * tcs_colors[0] +
gl_TessCoord.y * tcs_colors[1] +
gl_TessCoord.z * tcs_colors[2];
// ...
}
片段着色器：
in vec4 tes_colors;