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package com.google.skar;
import android.graphics.Matrix;
/**
* Provides static methods for matrix manipulation needed to draw in ARCore with Canvas.
* Input matrices are assumed to be 4x4 android.opengl.Matrix types (16-float arrays in column-major
* order).
* Output matrices are 3x3 android.graphics.Matrix types.
*/
public class CanvasMatrixUtil {
/******************* PUBLIC FUNCTIONS ***********************/
/**
* Returns an android.graphics.Matrix that can be used on a Canvas to draw a 2D object in
* perspective. Object will be rotated towards the XZ plane and will appear to stick on Planes.
* Undefined behavior when any of the matrices are not of size 16, or are null.
*
* @param model 4x4 model matrix of the object to be drawn (global/world)
* @param view 4x4 camera view matrix (brings objects to camera origin and
* orientation)
* @param projection 4x4 projection matrix
* @param viewPortWidth width of viewport of GLSurfaceView
* @param viewPortHeight height of viewport of GLSurfaceView
* @return 3x3 matrix that puts a 2D objects in perspective on a Canvas
*/
public static Matrix createPerspectiveMatrix(float[] model, float[] view, float[] projection,
float viewPortWidth, float viewPortHeight) {
float[] viewPort = createViewportMatrix(viewPortWidth, viewPortHeight);
float[] planeStickRotation = createXYtoXZRotationMatrix();
float[][] matrices = {planeStickRotation, model, view, projection, viewPort};
return createMatrixFrom4x4Array(matrices);
}
/**
* Returns a 16-float matrix in column-major order that represents a viewport matrix given
* the width and height of the viewport.
*
* @param width width of viewport
* @param height height of viewport
*/
public static float[] createViewportMatrix(float width, float height) {
float[] viewPort = new float[16];
android.opengl.Matrix.setIdentityM(viewPort, 0);
android.opengl.Matrix.translateM(viewPort, 0, width / 2, height / 2, 0);
android.opengl.Matrix.scaleM(viewPort, 0, width / 2, -height / 2, 0);
return viewPort;
}
/**
* Returns a 16-float matrix in column-major order that is used to rotate objects from the
* XY plane to the XZ plane. This is useful given that objects drawn on the Canvas are on the
* XY plane.
* In order to get objects to appear as if they are sticking on planes/ceilings/walls, we need
* to rotate them from the XY plane to the XZ plane.
*/
public static float[] createXYtoXZRotationMatrix() {
float[] rotation = new float[16];
android.opengl.Matrix.setIdentityM(rotation, 0);
android.opengl.Matrix.rotateM(rotation, 0, 90, 1, 0, 0);
return rotation;
}
/**
* Returns an android.graphics.Matrix resulting from a 16-float matrix array in column-major
* order.
* Undefined behavior when the array is not of size 16 or is null.
*
* @param m4 16-float matrix in column-major order
*/
public static Matrix createMatrixFrom4x4(float[] m4) {
float[] m3 = matrix4x4ToMatrix3x3(m4);
return createMatrixFrom3x3(m3);
}
/**
* Returns an android.graphics.Matrix resulting from the concatenation of 16-float matrices
* in column-major order from left to right.
* e.g: m4Array = {m1, m2, m3} --> returns m = m3 * m2 * m1
* Undefined behavior when the array is empty, null, or contains arrays not of size 9 (or null)
*
* @param m4Array array of 16-float matrices in column-major order
*/
public static Matrix createMatrixFrom4x4Array(float[][] m4Array) {
float[] result = multiplyMatrices4x4(m4Array);
return createMatrixFrom4x4(result);
}
/**
* Returns 4-float array resulting from the multiplication of a Vector of 4 floats
* with a 4x4 float Matrix. The return is essentially m4 * v4, with perspective-divide applied
* if perspectiveDivide is true
* @param m4 16-float matrix in column-major order
* @param v4 4-float vector
* @param perspectiveDivide if true, divide return value by the w-coordinate
* @return 4-float array resulting from the multiplication
*/
public static float[] multiplyMatrixVector(float[] m4, float[] v4, boolean perspectiveDivide) {
float[] result = new float[4];
android.opengl.Matrix.multiplyMV(result, 0, m4, 0, v4, 0);
if (perspectiveDivide) {
return new float[] {result[0] / result[3], result[1] / result[3],
result[2] / result[3], 1};
}
return new float[] {result[0], result[1], result[2], result[3]};
}
/**
* Returns a 16-float matrix in column-major order resulting from the multiplication of matrices
* e.g: m4Array = {m1, m2, m3} --> returns m = m3 * m2 * m1
* Undefined behavior when the array is empty, null, or contains arrays not of size 9 (or null)
*
* @param m4Array array of 16-float matrices in column-major order
*/
public static float[] multiplyMatrices4x4(float[][] m4Array) {
float[] result = new float[16];
android.opengl.Matrix.setIdentityM(result, 0);
float[] rhs = result;
for (int i = 0; i < m4Array.length; i++) {
float[] lhs = m4Array[i];
android.opengl.Matrix.multiplyMM(result, 0, lhs, 0, rhs, 0);
rhs = result;
}
return result;
}
/******************* PRIVATE FUNCTIONS ***********************/
/**
* Returns an android.graphics.Matrix resulting from a 9-float matrix array in row-major order.
* Undefined behavior when the array is not of size 9 or is null.
*
* @param m3 9-float matrix array in row-major order
*/
private static Matrix createMatrixFrom3x3(float[] m3) {
Matrix m = new Matrix();
m.setValues(m3);
return m;
}
/**
* Returns a 9-float matrix in row-major order given a 16-float matrix in column-major order.
* This will drop the Z column and row.
* Undefined behavior when the array is not of size 9 or is null.
*
* @param m4 16-float matrix in column-major order
*/
private static float[] matrix4x4ToMatrix3x3(float[] m4) {
float[] m3 = new float[9];
int j = 0;
for (int i = 0; i < 7; i = i + 3) {
if (j == 2) {
j++; //skip row #3
}
m3[i] = m4[j];
m3[i + 1] = m4[j + 4];
m3[i + 2] = m4[j + 12];
j++;
}
return m3;
}
}
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