LIBGDX版NEHE OPENGL- 6. Texture Mapping

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大概看过nehe的texture mapping代码之后,发现都是将一个纹理图片,按坐标映射的方式,来对应到点。

所以下面这段代码,对于了解这种映射方式的朋友来说,应该很好理解。

package com.kyugao.screen;import com.badlogic.gdx.Gdx;import com.badlogic.gdx.Screen;import com.badlogic.gdx.files.FileHandle;import com.badlogic.gdx.graphics.GL10;import com.badlogic.gdx.graphics.Mesh;import com.badlogic.gdx.graphics.PerspectiveCamera;import com.badlogic.gdx.graphics.Texture;import com.badlogic.gdx.graphics.VertexAttribute;import com.badlogic.gdx.graphics.VertexAttributes.Usage;public class TextureMapping implements Screen {private Mesh squareMesh;private PerspectiveCamera camera;private Texture texture;private float rquad = 0;@Overridepublic void render(float delta) {camera.update();camera.apply(Gdx.graphics.getGL10());Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);Gdx.gl.glEnable(GL10.GL_DEPTH_TEST);Gdx.gl.glEnable(GL10.GL_TEXTURE_2D);drawGLScene();rquad += 20f * delta; // 每秒钟转20度,计算在每一次render的时间差里,要转的角度。比如0.5秒,那就应该转10度。rquad %= 360;}private boolean drawGLScene() {Gdx.gl10.glLoadIdentity();Gdx.gl10.glTranslatef(0.0f, 0.0f, -7.0f);Gdx.gl10.glRotatef(rquad, 1.0f, 1.0f, 1.0f);Gdx.gl10.glTranslatef(0.0f, 0.0f, 7.0f);texture.bind();for (int i = 0; i < squareMesh.getMaxVertices() / 4; i++) {squareMesh.render(GL10.GL_TRIANGLE_FAN, i * 4, 4); // 正方形的6个面分别画出.}return true;}@Overridepublic void show() {squareMesh = new Mesh(true, 24, 24, new VertexAttribute(Usage.Position,3, "b_position"), new VertexAttribute(Usage.TextureCoordinates,2, "b_texture"));squareMesh.setVertices(new float[] {// Front face:-1f, 1.0f, -6.0f, 0f, 0f, // TL-1f, -1.0f, -6.0f, 0f, 1f, // BL1f, -1.0f, -6.0f, 1f, 1f, // BR1f, 1.0f, -6.0f, 1f, 0f, // TR// Top face:-1f, 1.0f, -8.0f, 0f, 0f, // LR-1f, 1.0f, -6.0f, 0f, 1f, // LN1f, 1.0f, -6.0f, 1f, 1f, // RN1f, 1.0f, -8.0f, 1f, 0f, // RR// Rear face1f, 1.0f, -8.0f, 0f, 0f, // TR1f, -1.0f, -8.0f, 0f, 1f, // BR-1f, -1.0f, -8.0f, 1f, 1f, // BL-1f, 1.0f, -8.0f, 1f, 0f, // TL// Bottom face-1f, -1.0f, -6.0f, 0f, 0f, // LN1f, -1.0f, -6.0f, 0f, 1f,// RN1f, -1.0f, -8.0f, 1f, 1f, // RR-1f, -1.0f, -8.0f, 1f, 0f, // LR// Left face-1f, 1.0f, -8.0f, 0f, 0f, // TR-1f, 1.0f, -6.0f, 0f, 1f, // TN-1f, -1.0f, -6.0f, 1f, 1f, // BN-1f, -1.0f, -8.0f, 1f, 0f, // BR// Right face1f, 1.0f, -6.0f, 0f, 0f, // TN1f, 1.0f, -8.0f, 1f, 0f, // TR1f, -1.0f, -8.0f, 1f, 1f, // BR1f, -1.0f, -6.0f, 0f, 1f // BN});squareMesh.setIndices(new short[] { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 });FileHandle imageFileHandle = Gdx.files.internal("data/NeHe.bmp");texture = new Texture(imageFileHandle);}@Overridepublic void hide() {}@Overridepublic void pause() {}@Overridepublic void resume() {}@Overridepublic void dispose() {}@Overridepublic void resize(int width, int height) {float aspectRatio = (float) width / (float) height;camera = new PerspectiveCamera(45, 2f * aspectRatio, 2f);}}

有一个gl的参数需要设置,这个是使用texture时需要的。

Gdx.gl.glEnable(GL10.GL_TEXTURE_2D);

再大概说一下纹理的映射:

// Front face:

-1f, 1.0f, -6.0f, 0f, 0f,// TL

-1f, -1.0f, -6.0f, 0f, 1f,// BL

1f, -1.0f, -6.0f, 1f, 1f,// BR

1f, 1.0f, -6.0f, 1f, 0f,// TR

以上坐标描述的是正方体前面(面对我们这一面)

每一行前三个数表示一个点的坐标,如:x=-1, y=1, z=-6.0.

接下来两个数表示的是这一点,对应纹理图片上的哪一点。

纹理图片,我们也用一个坐标来表示,那左上角为(0,0),右上角为(1,0),右下角为(1,1),左下角为(0,1)

所以,对应到正方形上就是,点TL(0,0)点BL(0,1)点BR(1,1)点TR(1,0)

于是,我们程序的效果就是:


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