OpenGL 纹理坐标错误

Question

使用我的答案，我已经成功地将整个字体图集呈现到屏幕上。但是，当涉及到从图集中渲染单个字符时，我的坐标似乎有些错误：

alt text http://img.condorcraft110.net/font%20renderer%20fail.png

据此（文本应该是 'Test font renderer text'）我可以假设纹理坐标是错误的。但是他们怎么错了？

完整的工作示例：

import java.awt.image.*;
import java.io.*;
import java.nio.*;
import javax.imageio.*;
import org.lwjgl.*;
import org.lwjgl.opengl.*;

public class OpenGLFontRendererTest
{
    private static int textureID;

    public static void main(String[] args) throws Exception
    {
        Display.setTitle("OpenGL Font Renderer Test");
        Display.setDisplayMode(new DisplayMode(640, 480));
        Display.create();

        GL11.glMatrixMode(GL11.GL_PROJECTION);
        GL11.glLoadIdentity();
        GL11.glOrtho(0, 640, 0, 480, 1, -1);
        GL11.glMatrixMode(GL11.GL_MODELVIEW);

        textureID = bindTextureFile("textures/font.png");

        while(!Display.isCloseRequested())
        {
            Display.sync(60);

            GL11.glClear(GL11.GL_COLOR_BUFFER_BIT | GL11.GL_DEPTH_BUFFER_BIT);
            GL11.glClearColor(0, 0, 0, 1);

            GL11.glColor4f(1, 1, 1, 1);
            drawText(20, 20, "Test font renderer text");

            Display.update();
        }

        Display.destroy();
    }

    private static void drawText(int x, int y, String text)
    {
        GL11.glPushMatrix();
            GL11.glTranslatef(x, y, 0);
            GL11.glDisable(GL11.GL_DEPTH_TEST);
            GL11.glEnable(GL11.GL_TEXTURE_2D);
            GL11.glEnable(GL11.GL_BLEND);
                GL11.glBlendFunc(GL11.GL_SRC_ALPHA, GL11.GL_ONE_MINUS_SRC_ALPHA);
                GL11.glBindTexture(GL11.GL_TEXTURE_2D, textureID);
                GL11.glBegin(GL11.GL_QUADS);
                    int xOff = 0;
                    int yOff = 0;
                    for(char c : text.toCharArray())
                    {
                        if(c == '\n')
                        {
                            xOff = 0;
                            yOff += 17;
                            continue;
                        }
                        else if(c == '\r')
                        {
                            xOff = 0;
                            continue;
                        }

                        float pos = (float)c;

                        float textureX = (pos % 16F) / 16F;
                        float textureY = (pos / 16F) / 16F;

                        GL11.glTexCoord2f(textureX, textureY + 0.0625F);
                        GL11.glVertex2i(xOff, yOff);

                        GL11.glTexCoord2f(textureX, textureY);
                        GL11.glVertex2i(xOff, yOff + 16);

                        GL11.glTexCoord2f(textureX + 0.0625F, textureY);
                        GL11.glVertex2i(xOff + 16, yOff + 16);

                        GL11.glTexCoord2f(textureX + 0.0625F, textureY + 0.0625F);
                        GL11.glVertex2i(xOff + 16, yOff);

                        xOff += 17;
                    }
                GL11.glEnd();
            GL11.glDisable(GL11.GL_BLEND);
            GL11.glDisable(GL11.GL_TEXTURE_2D);
            GL11.glEnable(GL11.GL_DEPTH_TEST);
        GL11.glPopMatrix();
    }

    private static int bindTextureFile(String file)
    {
        try
        {
            BufferedImage image = ImageIO.read(new FileInputStream(file));

            int[] pixels = new int[image.getWidth() * image.getHeight()];

            image.getRGB(0, 0, image.getWidth(), image.getHeight(), pixels, 0, image.getWidth());

            ByteBuffer buffer = BufferUtils.createByteBuffer(image.getWidth() * image.getHeight() * 4);

            for(int y = 0; y < image.getWidth(); y++)
            {
                for(int x = 0; x < image.getHeight(); x++)
                {
                    int pixel = pixels[y * image.getWidth() + x];

                    buffer.put((byte)((pixel >> 16) & 0xFF));
                    buffer.put((byte)((pixel >> 8) & 0xFF));
                    buffer.put((byte)(pixel & 0xFF));
                    buffer.put((byte)((pixel >> 24) & 0xFF));
                }
            }

            buffer.flip();

            int textureID = GL11.glGenTextures();

            GL11.glBindTexture(GL11.GL_TEXTURE_2D, textureID);

            GL11.glTexParameteri(GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_WRAP_S, GL12.GL_CLAMP_TO_EDGE);
            GL11.glTexParameteri(GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_WRAP_T, GL12.GL_CLAMP_TO_EDGE);

            GL11.glTexParameteri(GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_MIN_FILTER, GL11.GL_NEAREST);
            GL11.glTexParameteri(GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_MAG_FILTER, GL11.GL_NEAREST);

            GL11.glTexImage2D(GL11.GL_TEXTURE_2D, 0, GL11.GL_RGBA, image.getWidth(), image.getHeight(), 0, GL11.GL_RGBA, GL11.GL_UNSIGNED_BYTE, buffer);

            return textureID;
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }

        return -1;
    }
}

font.png 再次是用于测试目的的默认 Minecraft 字体文件 (/fonts/default.png)。

Answer 1

好的，我设法解决了这个问题。我按浮点数划分，所以我得到了小数位，这弄乱了坐标。

修改后的代码：

import java.awt.image.*;
import java.io.*;
import java.nio.*;
import javax.imageio.*;
import org.lwjgl.*;
import org.lwjgl.opengl.*;

public class OpenGLFontRendererTest
{
    private static int textureID;

    public static void main(String[] args) throws Exception
    {
        Display.setTitle("OpenGL Font Renderer Test");
        Display.setDisplayMode(new DisplayMode(640, 480));
        Display.create();

        GL11.glMatrixMode(GL11.GL_PROJECTION);
        GL11.glLoadIdentity();
        GL11.glOrtho(0, 640, 0, 480, 1, -1);
        GL11.glMatrixMode(GL11.GL_MODELVIEW);

        textureID = bindTextureFile("textures/font.png");

        while(!Display.isCloseRequested())
        {
            Display.sync(60);

            GL11.glClear(GL11.GL_COLOR_BUFFER_BIT | GL11.GL_DEPTH_BUFFER_BIT);
            GL11.glClearColor(0, 0, 0, 1);

            GL11.glColor4f(1, 1, 1, 1);
            drawText(20, 20, "Test font renderer text");

            Display.update();
        }

        Display.destroy();
    }

    private static void drawText(int x, int y, String text)
    {
        GL11.glPushMatrix();
            GL11.glTranslatef(x, y, 0);
            GL11.glDisable(GL11.GL_DEPTH_TEST);
            GL11.glEnable(GL11.GL_TEXTURE_2D);
            GL11.glEnable(GL11.GL_BLEND);
                GL11.glBlendFunc(GL11.GL_SRC_ALPHA, GL11.GL_ONE_MINUS_SRC_ALPHA);
                GL11.glBindTexture(GL11.GL_TEXTURE_2D, textureID);
                GL11.glBegin(GL11.GL_QUADS);
                    int xOff = 0;
                    int yOff = 0;
                    for(char c : text.toCharArray())
                    {
                        if(c == '\n')
                        {
                            xOff = 0;
                            yOff -= 17;
                            continue;
                        }
                        else if(c == '\r')
                        {
                            xOff = 0;
                            continue;
                        }

                        int pos = (int)c; // THESE

                        float textureX = (float)(pos % 16F) / 16F; // THREE
                        float textureY = (float)(pos / 16) / 16F; // LINES

                        GL11.glTexCoord2f(textureX, textureY + 0.0625F);
                        GL11.glVertex2i(xOff, yOff);

                        GL11.glTexCoord2f(textureX, textureY);
                        GL11.glVertex2i(xOff, yOff + 16);

                        GL11.glTexCoord2f(textureX + 0.0625F, textureY);
                        GL11.glVertex2i(xOff + 16, yOff + 16);

                        GL11.glTexCoord2f(textureX + 0.0625F, textureY + 0.0625F);
                        GL11.glVertex2i(xOff + 16, yOff);

                        xOff += 17;
                    }
                GL11.glEnd();
            GL11.glDisable(GL11.GL_BLEND);
            GL11.glDisable(GL11.GL_TEXTURE_2D);
            GL11.glEnable(GL11.GL_DEPTH_TEST);
        GL11.glPopMatrix();
    }

    private static int bindTextureFile(String file)
    {
        try
        {
            BufferedImage image = ImageIO.read(new FileInputStream(file));

            int[] pixels = new int[image.getWidth() * image.getHeight()];

            image.getRGB(0, 0, image.getWidth(), image.getHeight(), pixels, 0, image.getWidth());

            ByteBuffer buffer = BufferUtils.createByteBuffer(image.getWidth() * image.getHeight() * 4);

            for(int y = 0; y < image.getWidth(); y++)
            {
                for(int x = 0; x < image.getHeight(); x++)
                {
                    int pixel = pixels[y * image.getWidth() + x];

                    buffer.put((byte)((pixel >> 16) & 0xFF));
                    buffer.put((byte)((pixel >> 8) & 0xFF));
                    buffer.put((byte)(pixel & 0xFF));
                    buffer.put((byte)((pixel >> 24) & 0xFF));
                }
            }

            buffer.flip();

            int textureID = GL11.glGenTextures();

            GL11.glBindTexture(GL11.GL_TEXTURE_2D, textureID);

            GL11.glTexParameteri(GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_WRAP_S, GL12.GL_CLAMP_TO_EDGE);
            GL11.glTexParameteri(GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_WRAP_T, GL12.GL_CLAMP_TO_EDGE);

            GL11.glTexParameteri(GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_MIN_FILTER, GL11.GL_NEAREST);
            GL11.glTexParameteri(GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_MAG_FILTER, GL11.GL_NEAREST);

            GL11.glTexImage2D(GL11.GL_TEXTURE_2D, 0, GL11.GL_RGBA, image.getWidth(), image.getHeight(), 0, GL11.GL_RGBA, GL11.GL_UNSIGNED_BYTE, buffer);

            return textureID;
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }

        return -1;
    }
}

OpenGL 纹理坐标错误

OpenGL texture coordinates wrong

java

opengl

lwjgl