[英]Why is my rotation matrix giving an extra translation?
幾周前,我決定制作自己的簡單3D游戲引擎。 我在網上看了幾個教程,看了很多視頻,到目前為止,我已經得到了很好的引擎。 但我有一個問題。 當我旋轉或縮放對象時,它的中心似乎是屏幕的左上角而不是它的真實中心。 例如,當我旋轉一個物體時,它會圍繞屏幕的左邊緣旋轉,當我縮放它時,它會朝向屏幕的角落或遠離屏幕的角落。 這是我的代碼:
網格類
package com.cub.cubefront.mesh;
import com.cub.cubefront.math.Matrix4f;
import com.cub.cubefront.math.Vector3f;
public class Mesh {
private Vector3f[] verts;
private Vector3f center;
private double rotX = 0;
private double rotY = 0;
private double rotZ = 0;
private double scaleX = 1;
private double scaleY = 1;
private double scaleZ = 1;
private double translateX = 0;
private double translateY = 0;
private double translateZ = 0;
public Mesh(int arg0) {
verts = new Vector3f[arg0];
}
public Vector3f getVertexAt(int arg0) {
return verts[arg0 - 1];
}
public Vector3f[] getVerticies() {
return verts;
}
public int getVerticiesCount() {
return verts.length;
}
public void setVertexAt(int arg0, Vector3f arg1) {
verts[arg0 - 1] = arg1;
}
public void setRotationPoint(Vector3f arg0) {
this.center = arg0;
}
public Vector3f getRotationPoint() {
return center;
}
public Vector3f getCenter() {
int arg0 = verts.length;
double centerX = 0;
double centerY = 0;
double centerZ = 0;
for (int i = 0; i < arg0; i++) {
centerX += verts[i].getX();
centerY += verts[i].getY();
centerZ += verts[i].getZ();
}
return new Vector3f((float)(centerX / arg0), (float)(centerY / arg0), (float)(centerZ / arg0));
}
public void rotateX(double arg0) {
this.rotX += Math.toRadians(arg0);
}
public void setRotationX(double arg0) {
this.rotX = Math.toRadians(arg0);
}
public Matrix4f getXRotationAsMatrix() {
return new Matrix4f(new double[][] { // YZ rotation matrix (X)
{ 1, 0, 0, 0 },
{ 0, Math.cos(rotX), Math.sin(rotX), 0 },
{ 0, -Math.sin(rotX), Math.cos(rotX), 0 },
{ 0, 0, 0, 1 }
});
}
public Matrix4f getZRotationAsMatrix() {
return new Matrix4f(new double[][] { // XY rotation matrix (Z)
{ Math.cos(rotZ), -Math.sin(rotZ), 0, 0 },
{ Math.sin(rotZ), Math.cos(rotZ), 0, 0 },
{ 0, 0, 1, 0 },
{ 0, 0, 0, 1 }
});
}
public void rotateY(double arg0) {
this.rotY += Math.toRadians(arg0);
}
public void setRotationY(double arg0) {
this.rotY = Math.toRadians(arg0);
}
public Matrix4f getYRotationAsMatrix() {
return new Matrix4f(new double[][] { // XZ rotation matrix (Y)
{ Math.cos(rotY), 0, Math.sin(rotY), 0 },
{ 0, 1, 0, 0 },
{ -Math.sin(rotY), 0, Math.cos(rotY), 0},
{ 0, 0, 0, 1 }
});
}
public void setRotationZ(double arg0) {
this.rotZ = Math.toRadians(arg0);
}
public void rotateZ(double arg0) {
this.rotZ += Math.toRadians(arg0);
}
public Matrix4f getRotation() {
return getZRotationAsMatrix().multiply(getXRotationAsMatrix()).multiply(getYRotationAsMatrix());
}
public void setScaleX(double arg0) {
this.scaleX = arg0;
}
public void scaleX(double arg0) {
this.scaleX += arg0;
}
public double getScaleX() {
return scaleX;
}
public void setScaleY(double arg0) {
this.scaleY = arg0;
}
public void scaleY(double arg0) {
this.scaleY += arg0;
}
public double getScaleY() {
return scaleY;
}
public void setScaleZ(double arg0) {
this.scaleZ = arg0;
}
public void scaleZ(double arg0) {
this.scaleZ += arg0;
}
public double getScaleZ() {
return scaleZ;
}
public void setScale(double arg0) {
setScaleX(arg0);
setScaleY(arg0);
setScaleZ(arg0);
}
public void setScale(double[][] arg0) {
this.scaleX = arg0[0][0];
this.scaleY = arg0[1][1];
this.scaleZ = arg0[2][2];
}
public void setScale(Matrix4f arg0) {
this.scaleX = arg0.getValueAt(0, 0);
this.scaleY = arg0.getValueAt(1, 1);
this.scaleZ = arg0.getValueAt(2, 2);
}
public void scale(double arg0) {
scaleX(arg0);
scaleY(arg0);
scaleZ(arg0);
}
public Matrix4f getScale() {
return new Matrix4f(new double[][] {
{ getScaleX(), 0, 0, 0 },
{ 0, getScaleY(), 0, 0 },
{ 0, 0, getScaleZ(), 0 },
{ 0, 0, 0, 1 }
});
}
public void translateX(double arg0) {
this.translateX += arg0;
}
public void translateY(double arg0) {
this.translateY += arg0;
}
public void translateZ(double arg0) {
this.translateZ += arg0;
}
public Matrix4f getTranslation() {
return new Matrix4f(new double[][] {
{ 1, 0, 0, translateX },
{ 0, 1, 0, translateY },
{ 0, 0, 1, translateZ },
{ 0, 0, 0, 1 }
});
}
}
場景類
package com.cub.cubefront;
import com.cub.cubefront.graphics.Bitmap;
import com.cub.cubefront.input.InputHandler;
import com.cub.cubefront.math.Matrix4f;
import com.cub.cubefront.math.Vector2f;
import com.cub.cubefront.math.Vector3f;
import com.cub.cubefront.mesh.Camera;
import com.cub.cubefront.mesh.Mesh;
public class Scene extends Bitmap {
private Camera defaultCam;
public InputHandler input = new InputHandler();
public Scene() {
super(MainEngine.getWidth(), MainEngine.getHeight());
defaultCam = new Camera();
}
public void update() { }
public void start() { }
public void render() { }
public void render(Mesh arg0) {
Matrix4f trans = arg0.getRotation().multiply(arg0.getScale().multiply(arg0.getTranslation()));
for (int i = 1; i < arg0.getVerticiesCount()+1; i++) { // Depth: Manipulate x and y with z
Vector3f v1 = trans.transform(arg0.getVertexAt(i));
for (int n = 1; n < i; n++) {
Vector3f v2 = trans.transform(arg0.getVertexAt(n));
drawLine(
new Vector2f((v1.getX()), (v1.getY())),
new Vector2f((v2.getX()), (v2.getY()))
);
}
}
}
public void clear() {
for (int i = 0; i < pixels.length; i++) {
pixels[i] = 0;
}
}
public Camera getCamera() {
return defaultCam;
}
public void setCamera(Camera defaultCam) {
this.defaultCam = defaultCam;
}
}
Matrix4f類
package com.cub.cubefront.math;
public class Matrix4f {
private double[][] values;
public Matrix4f() {
values = new double[4][4];
setValues();
}
public Matrix4f(double[][] arg0) {
setValues(arg0);
}
private Matrix4f setValues() {
values[0][0] = 1; values[0][1] = 0; values[0][2] = 0; values[0][3] = 0;
values[1][0] = 0; values[1][1] = 1; values[1][2] = 0; values[1][3] = 0;
values[2][0] = 0; values[2][1] = 0; values[2][2] = 1; values[2][3] = 0;
values[3][0] = 0; values[3][1] = 0; values[3][2] = 0; values[3][3] = 1;
return this;
}
public Matrix4f multiply(Matrix4f arg0) {
double res[][] = new double[4][4];
for (int i = 0; i < 4; i++) {
for (int j = 0; j < 4; j++) {
for (int k = 0; k < 4; k++) {
res[i][j] += values[i][k] * arg0.getValueAt(k, j);
}
}
}
return new Matrix4f(res);
}
public double[][] getValues() {
return values;
}
public double getValueAt(int arg0, int arg1) {
return values[arg0][arg1];
}
public void setValues(double[][] arg0) {
this.values = arg0;
}
public void setValueAt(int arg0, int arg1, double arg2) {
values[arg0][arg1] = arg2;
}
public Vector3f transform(Vector3f arg0) {
return new Vector3f(
(float)(arg0.getX() * values[0][0] + arg0.getY() * values[1][0] + arg0.getZ() * values[2][0]),
(float)(arg0.getX() * values[0][1] + arg0.getY() * values[1][1] + arg0.getZ() * values[2][1]),
(float)(arg0.getY() * values[0][2] + arg0.getY() * values[1][2] + arg0.getZ() * values[2][2])
);
}
}
如果你還不知道我的意思,請看這些圖片。
圖片1:
圖片#2:
你看到它是如何圍繞角落而不是它的中心旋轉的嗎? 感謝您努力提供幫助!
這種情況通常發生在您進行轉換而不將對象重置為Origin之后才會影響它。 請記住,Matrix訂單很重要。 旋轉相對於原點發生,因此如果您的對象不在原點上,那么它將奇怪地旋轉。
在將其翻譯為(0,0,0)
后嘗試旋轉它。 然后將所需的平移應用於三角形(即轉換為原點,旋轉,返回原始位置)。
希望能幫助到你。
編輯
通常,如果要圍繞固定點旋轉多邊形,則應該以所需點(0,0,0)
方式平移多邊形。 然后繼續旋轉,最后返回原始位置。
假設你有一個帶頂點(1,1)
, (3,1)
和(2,3)
的三角形。 如果你想圍繞該三角形的中心 (即(2,2)
)旋轉,你應該:
(2,2)
(使(2,2)
原點) (2,2)
,返回原始位置。 同樣的原則適用於3維度。
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