c - 过剩 reshape 功能不起作用

Question

当我尝试调整过剩窗口的大小时，屏幕变为空白。

这是 reshape 回调函数的代码:

void Resize(int width, int height) 
{  
    CurrentWidth = width;
    CurrentHeight = height;


    glViewport(0, 0, (GLsizei)CurrentWidth, (GLsizei)CurrentHeight); 

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity(); 
    glOrtho(0, CurrentWidth, CurrentHeight, 0, NearPlane, FarPlane);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    glutPostRedisplay();
}

我对 opengl 世界还很陌生，但据我所知，这应该是可行的。

这是所有代码的组合:

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <GL/glew.h>
#include <GL/freeglut.h>
#include <gl/glut.h>

#include "Utils.h"

int LEFT = 0;
int RIGHT = 0;
int UP = 0;
int DOWN = 0;

int CurrentWidth = 800,
    CurrentHeight = 800,
    WindowHandle = 0;

float NearPlane = 1.0f,
      FarPlane = 100.0f;

float lightX,
      lightY;

void Initialize(int, char*[]);
void InitWindow(int, char*[]);
void Idle(void);
void Resize(int, int);
void KeyPressed(unsigned char, int, int);
void SpecialPressed(int, int, int);
void SpecialReleased(int, int, int);
void Update(void);
void Render(void);
void FillZBuffer(void);
void ClearAlpha(void);
void RenderLightAlpha(float);
void GeometryPass(void);
void Draw(void);

int main (int argc, char* argv[]) 
{  
    Initialize(argc, argv);

    glutMainLoop(); 

    exit(EXIT_SUCCESS);
}

void Initialize(int argc, char* argv[])
{
    InitWindow(argc, argv);

    fprintf(
        stdout,
        "INFO: OpenGL Version: %s\n",
        glGetString(GL_VERSION)
    );

    lightX = 300.0f;
    lightY = 300.0f;
}

void InitWindow(int argc, char* argv[])
{
    glutInit(&argc, argv);

    glutInitContextVersion(3, 3);
    glutInitContextProfile(GLUT_COMPATIBILITY_PROFILE);

    glutSetOption(
        GLUT_ACTION_ON_WINDOW_CLOSE,
        GLUT_ACTION_GLUTMAINLOOP_RETURNS
    );

    glutInitWindowSize (CurrentWidth, CurrentHeight); 
    glutInitWindowPosition (100, 100);

    glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGBA | GLUT_ALPHA);

    WindowHandle = glutCreateWindow ("Shadows");  

    if(WindowHandle < 1) {
        fprintf(
            stderr,
            "ERROR: Could not create a new rendering window.\n"
        );
        exit(EXIT_FAILURE);
    }

    glutDisplayFunc(Render); 
    glutReshapeFunc(Resize);
    glutIdleFunc(Idle);
    glutKeyboardFunc(KeyPressed);
    glutSpecialFunc(SpecialPressed);
    glutSpecialUpFunc(SpecialReleased);
} 

void Update()
{
    int speed = 10;
    if (LEFT)
    {
        lightX -= speed;
    }
    if (RIGHT)
    {
        lightX += speed;
    }
    if (UP)
    {
        lightY -= speed;
    }
    if (DOWN)
    {
        lightY += speed;
    }
}

void Draw()
{
    float x = 200;
    float y = 200;
    float w = 100;
    float h = 100;
    float depth = 0.0f;

    // floor
    glColor4f(0.5f, 0.5f, 0.5f, 1.0f);
    depth = -10.0f;
    glBegin(GL_QUADS);
    {
        glVertex3f(0, 0, depth);
        glVertex3f((float)CurrentWidth, 0, depth);
        glVertex3f((float)CurrentWidth, (float)CurrentHeight, depth);
        glVertex3f(0, (float)CurrentHeight, depth);
    }
    glEnd();

    // square
    glColor4f(1.0f, 0.0f, 0.0f, 1.0f);
    depth = -5.0;
    glBegin(GL_QUADS);
    {
        glVertex3f( x,  y, depth);
        glVertex3f( x + w, y, depth);
        glVertex3f(x + w, y + h, depth);
        glVertex3f(x,  y + h, depth);
    }
    glEnd();
}

void Render() 
{
    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glDisable(GL_CULL_FACE);

    Update();

    FillZBuffer();

    ClearAlpha();

    RenderLightAlpha(1.0f);

    GeometryPass();

    glutSwapBuffers();
    glutPostRedisplay(); 
}  

void FillZBuffer()
{
    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_LESS);
    glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
    glDepthMask(GL_TRUE);

    Draw();

    glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
    glDepthMask(GL_FALSE);
}

void ClearAlpha()
{
    glDisable(GL_BLEND);
    glDisable(GL_DEPTH_TEST);
    glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_TRUE);
    glColor4f(0.0f, 0.0f, 0.0f, 0.0f);

    glBegin (GL_QUADS);
    {
        glVertex2f(0, 0);
        glVertex2f((float)CurrentWidth, 0);
        glVertex2f((float)CurrentWidth, (float)CurrentHeight);
        glVertex2f(0, (float)CurrentHeight);
    }
    glEnd ();
}

void RenderLightAlpha(float intensity)
{
    float depth = -1.0f;  
    float radius = 300.0f;
    float angle;
    int numSubdivisions = 32;

    glDisable(GL_BLEND);
    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_LEQUAL);

    glBegin(GL_TRIANGLE_FAN);
    {
        glColor4f(0.0f, 0.0f, 0.0f,  intensity);
        glVertex3f(lightX, lightY, depth);

        // Set edge colour for rest of shape
        glColor4f(0.0f, 0.0f, 0.0f, 0.0f);

        for (angle = 0; angle <= (float)PI * 2; angle += (((float)PI * 2) / numSubdivisions))
        {
            glVertex3f( radius*(float)cos(angle) + lightX, radius*(float)sin(angle) + lightY, depth);  
        }

        glVertex3f(lightX + radius, lightY, depth);
    }
    glEnd();
}

void GeometryPass()
{
    glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_LEQUAL);
    glEnable(GL_BLEND);
    glBlendFunc(GL_DST_ALPHA, GL_ONE);

    Draw();
}

void Idle()
{
    glutPostRedisplay();
}

void Resize(int width, int height) 
{  
    CurrentWidth = width;
    CurrentHeight = height;


    glViewport(0, 0, (GLsizei)CurrentWidth, (GLsizei)CurrentHeight); 

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity(); 
    glOrtho(0, CurrentWidth, CurrentHeight, 0, NearPlane, FarPlane);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    glutPostRedisplay();
}

void KeyPressed(unsigned char key, int x, int y)
{
    UNREFERENCED_PARAMETER(x);
    UNREFERENCED_PARAMETER(y);

    // escape key
    if (key == 27)
    {
        exit(0);
    }
}

void SpecialPressed(int keyCode, int x, int y)
{
    UNREFERENCED_PARAMETER(x);
    UNREFERENCED_PARAMETER(y);

    if (keyCode == GLUT_KEY_LEFT)
    {
        LEFT = 1;
    }
    else if (keyCode == GLUT_KEY_RIGHT)
    {
        RIGHT = 1;
    }
    else if (keyCode == GLUT_KEY_UP)
    {
        UP = 1;
    }
    else if (keyCode == GLUT_KEY_DOWN)
    {
        DOWN = 1;
    }
}

void SpecialReleased(int keyCode, int x, int y)
{
    UNREFERENCED_PARAMETER(x);
    UNREFERENCED_PARAMETER(y);
    if (keyCode == GLUT_KEY_LEFT)
    {
        LEFT = 0;
    }
    else if (keyCode == GLUT_KEY_RIGHT)
    {
        RIGHT = 0;
    }
    else if (keyCode == GLUT_KEY_UP)
    {
        UP = 0;
    }
    else if (keyCode == GLUT_KEY_DOWN)
    {
        DOWN = 0;
    }
}

如果您需要更多信息，请告诉我。

Answer 1

在 FillZBuffer 函数中，深度掩模在末尾被禁用，并且仅在同一函数的开头重新启用。因此，当再次调用 Render 时，清除深度缓冲区位的调用不会执行任何操作，因为深度掩模已被禁用。

要解决此问题，必须在调用清除深度缓冲区位之前重新启用深度掩码。

这就是渲染应该的样子。

void Render() 
{
    glDepthMask(GL_TRUE); // insert this line
    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glDisable(GL_CULL_FACE);

    Update();

    FillZBuffer();

    ClearAlpha();

    RenderLightAlpha(1.0f);

    GeometryPass();

    glutSwapBuffers();
    glutPostRedisplay(); 
}