LWJGL教程08 - 变换

透视投影

当改变z坐标时，渲染的矩形并没有大小上的变化。

是由于x，y坐标没有改变。

其中
$$
\alpha = \frac{W_w}{W_h}
$$
暂时先不推导。

使用JOML处理LWJGL内的数学运算。

<dependency>
    <groupId>org.joml</groupId>
    <artifactId>joml</artifactId>
    <version>${joml.version}</version>
</dependency>

<properties>
    [...]
    <joml.version>1.9.6</joml.version>
    [...]
</properties>

先创建Projection类。

[imports ...]

public class Projection {

    private static final float FOV = (float) Math.toRadians(60.0f);
    private static final float Z_FAR = 1000.f;
    private static final float Z_NEAR = 0.01f;

    private Matrix4f projectionMatrix;

    public Projection(int width, int height) {
        projectionMatrix = new Matrix4f();
        updateProjectionMatrix(width, height);
    }

    public void updateProjectionMatrix(int width, int height) {
        float aspectRatio = (float) width / height;
        projectionMatrix = new Matrix4f().perspective(FOV, aspectRatio,
                Z_NEAR, Z_FAR);
    }

    public Matrix4f getProjectionMatrix() {
        return projectionMatrix;
    }

}

并修改一下vertex.vert。

#version 330

layout (location=0) in vec3 position;
layout (location=1) in vec3 inColour;

out vec3 exColour;

uniform mat4 projectionMatrix;

void main()
{
    gl_Position = projectionMatrix * vec4(position, 1.0);
    exColour = inColour;
}

再创建UniformsMap。

[imports ...]

import static org.lwjgl.opengl.GL20.*;

public class UniformsMap {
    private Map<String, Integer> uniforms;
    private int programId;

    public UniformsMap(int programId) {
        uniforms = new HashMap<>();
        this.programId = programId;
    }

    public void createUniform(String uniformName) {
        int uniformLocation = glGetUniformLocation(programId, uniformName);
        if (uniformLocation < 0)
            throw new RuntimeException("Could not find uniform: " + uniformName);
        uniforms.put(uniformName, uniformLocation);
    }

    public void setUniform(String uniformName, Matrix4f value) {
        // 转储矩阵到FloatBuffer
        try (MemoryStack stack = MemoryStack.stackPush()) {
            FloatBuffer floatBuffer = stack.mallocFloat(16);
            value.get(floatBuffer);
            glUniformMatrix4fv(uniforms.get(uniformName), false, floatBuffer);
        }
    }
}

方便起见，将Scene渲染的工作交给SceneRender，整理一下Render的代码。

[imports ...]

public class SceneRender {
    UniformsMap uniforms;

    public SceneRender() {
        [...]
        
        shaderProgram.link();
        uniforms = new UniformsMap(shaderProgram.getProgramId());
        uniforms.createUniform("projectionMatrix");
    }

    public void render(Scene scene) {
        shaderProgram.bind();

        uniforms.setUniform("projectionMatrix", scene.getProjection().getProjectionMatrix());

        [...]
    }
    
    [...]
}

再在Scene的构造函数中实例化Projection。

public Scene() {
    projection = new Projection(Window.getWidth(), Window.getHeight());
}

并让每一次窗口改变大小时调用Projection.updateProjectionMatrix()

最后测试一下。

[imports ...]

public class TestLogic implements ILogic {

    @Override
    public void init() {
        float[] vertices = new float[] {
                -0.5f,  0.5f, -1.05f,      // v1
                -0.5f, -0.5f, -1.05f,      // v2
                 0.5f,  0.5f, -1.05f,      // v3
                 0.5f, -0.5f, -1.05f,      // v4
        };
        
        [...]
    }
    
    [...]
}

改变一下图像的z坐标。

[imports ...]

public class TestLogic implements ILogic {

    @Override
    public void init() {
        float[] vertices = new float[] {
                -0.5f,  0.5f, -1.05f,      // v1
                -0.5f, -0.5f, -2.05f,      // v2
                 0.5f,  0.5f, -1.05f,      // v3
                 0.5f, -0.5f, -2.05f,      // v4
        };
        
        [...]
    }
    
    [...]
}

---

随便整点有趣的。

@Override
public void init() {
    float[] vertices = new float[] {
             0.0f ,  0.5f , -1.05f,    // v0
             0.5f ,  0.3f , -1.05f,    // v1
             0.5f , -0.3f , -1.05f,    // v2
             0.0f , -0.5f , -1.05f,    // v3
            -0.5f , -0.3f , -1.05f,     // v4
            -0.5f ,  0.3f , -1.05f,     // v5
             0.0f ,  0.1f , -1.05f,     // v6
    };
    float[] colors = new float[]{
            0.0f, 0.0f, 1.0f,
            1.0f, 0.0f, 1.0f,
            1.0f, 0.0f, 0.0f,
            1.0f, 1.0f, 0.0f,
            0.0f, 1.0f, 0.0f,
            0.0f, 1.0f, 1.0f,
            1.0f, 1.0f, 1.0f,
    };
    int[] indices = new int[] {
            1, 0, 6,
            2, 1, 6,
            3, 2, 6,
            4, 3, 6,
            5, 4, 6,
            0, 5, 6
    };

    Mesh mesh = new Mesh(vertices, colors, indices);
    Engine.scene.addMesh(mesh);
}