Improve rsMatrix* documentation, fix bugs
Improves the user-facing documentation. Fix the incorrect row & column
naming on the Get/Set API. Fix a bug where rsMatrixLoadMultiply could
not have the destination be one of the source,
e.g. rsMatrixLoadMultiply(&l, &l, &r)
Change-Id: I42207aacf4ebe815d4a79db2aaa9c44f85864696
diff --git a/scriptc/rs_matrix.rsh b/scriptc/rs_matrix.rsh
index ebff7f4..34b9532 100644
--- a/scriptc/rs_matrix.rsh
+++ b/scriptc/rs_matrix.rsh
@@ -15,8 +15,35 @@
*/
/** @file rs_matrix.rsh
- * \brief Matrix routines
+ * \brief Matrix functions.
*
+ * These functions let you manipulate square matrices of rank 2x2, 3x3, and 4x4.
+ * They are particularly useful for graphical transformations and are
+ * compatible with OpenGL.
+ *
+ * A few general notes:
+ *
+ * \li We use a zero-based index for rows and columns. E.g. the last element of
+ * a \ref rs_matrix4x4 is found at (3, 3).
+ *
+ * \li RenderScript uses column-based vectors. Transforming a vector is done by
+ * postmultiplying the vector, e.g. <em>(matrix * vector)</em>, as provided by
+ * \ref rsMatrixMultiply.
+ *
+ * \li To create a transformation matrix that performs two transformations at
+ * once, multiply the two source matrices, with the first transformation as the
+ * right argument. E.g. to create a transformation matrix that applies the
+ * transformation \e s1 followed by \e s2, call
+ * </c>rsMatrixLoadMultiply(&combined, &s2, &s1)</c>.
+ * This derives from <em>s2 * (s1 * v)</em>, which is <em>(s2 * s1) * v</em>.
+ *
+ * \li We have two style of functions to create transformation matrices:
+ * rsMatrixLoad<em>Transformation</em> and rsMatrix<em>Transformation</em>. The
+ * former style simply stores the transformation matrix in the first argument.
+ * The latter modifies a pre-existing transformation matrix so that the new
+ * transformation happens first. E.g. if you call \ref rsMatrixTranslate
+ * on a matrix that already does a scaling, the resulting matrix when applied
+ * to a vector will first do the translation then the scaling.
*
*/
@@ -24,54 +51,60 @@
#define __RS_MATRIX_RSH__
/**
- * Set one element of a matrix.
+ * Set an element of a matrix.
*
- * @param m The matrix to be set
- * @param row
- * @param col
- * @param v
+ * @param m The matrix that will be modified.
+ * @param col The zero-based column of the element to be set.
+ * @param row The zero-based row of the element to be set.
+ * @param v The value to set.
+ *
+ * \warning The order of the column and row parameters may be
+ * unexpected.
*
* @return void
*/
_RS_RUNTIME void __attribute__((overloadable))
-rsMatrixSet(rs_matrix4x4 *m, uint32_t row, uint32_t col, float v);
+rsMatrixSet(rs_matrix4x4 *m, uint32_t col, uint32_t row, float v);
/**
* \overload
*/
_RS_RUNTIME void __attribute__((overloadable))
-rsMatrixSet(rs_matrix3x3 *m, uint32_t row, uint32_t col, float v);
+rsMatrixSet(rs_matrix3x3 *m, uint32_t col, uint32_t row, float v);
/**
* \overload
*/
_RS_RUNTIME void __attribute__((overloadable))
-rsMatrixSet(rs_matrix2x2 *m, uint32_t row, uint32_t col, float v);
+rsMatrixSet(rs_matrix2x2 *m, uint32_t col, uint32_t row, float v);
/**
- * Get one element of a matrix.
+ * Returns one element of a matrix.
*
- * @param m The matrix to read from
- * @param row
- * @param col
+ * @param m The matrix to extract the element from.
+ * @param col The zero-based column of the element to be extracted.
+ * @param row The zero-based row of the element to extracted.
+ *
+ * \warning The order of the column and row parameters may be
+ * unexpected.
*
* @return float
*/
_RS_RUNTIME float __attribute__((overloadable))
-rsMatrixGet(const rs_matrix4x4 *m, uint32_t row, uint32_t col);
+rsMatrixGet(const rs_matrix4x4 *m, uint32_t col, uint32_t row);
/**
* \overload
*/
_RS_RUNTIME float __attribute__((overloadable))
-rsMatrixGet(const rs_matrix3x3 *m, uint32_t row, uint32_t col);
+rsMatrixGet(const rs_matrix3x3 *m, uint32_t col, uint32_t row);
/**
* \overload
*/
_RS_RUNTIME float __attribute__((overloadable))
-rsMatrixGet(const rs_matrix2x2 *m, uint32_t row, uint32_t col);
+rsMatrixGet(const rs_matrix2x2 *m, uint32_t col, uint32_t row);
/**
* Set the elements of a matrix to the identity matrix.
*
- * @param m
+ * @param m The matrix to set.
*/
extern void __attribute__((overloadable)) rsMatrixLoadIdentity(rs_matrix4x4 *m);
/**
@@ -86,7 +119,13 @@
/**
* Set the elements of a matrix from an array of floats.
*
- * @param m
+ * The array of floats should be in row-major order, i.e. the element a
+ * <em>row 0, column 0</em> should be first, followed by the element at
+ * <em>row 0, column 1</em>, etc.
+ *
+ * @param m The matrix to set.
+ * @param v The array of values to set the matrix to. These arrays should be
+ * 4, 9, or 16 floats long, depending on the matrix size.
*/
extern void __attribute__((overloadable)) rsMatrixLoad(rs_matrix4x4 *m, const float *v);
/**
@@ -98,18 +137,29 @@
*/
extern void __attribute__((overloadable)) rsMatrixLoad(rs_matrix2x2 *m, const float *v);
/**
- * \overload
+ * Set the elements of a matrix from another matrix.
+ *
+ * If the source matrix is smaller than the destination, the rest of the
+ * destination is filled with elements of the identity matrix. E.g.
+ * loading a rs_matrix2x2 into a rs_matrix4x4 will give:
+ *
+ * \htmlonly<table>
+ * <tr><td>m00</td><td>m01</td><td>0.0</td><td>0.0</td></tr>
+ * <tr><td>m10</td><td>m11</td><td>0.0</td><td>0.0</td></tr>
+ * <tr><td>0.0</td><td>0.0</td><td>1.0</td><td>0.0</td></tr>
+ * <tr><td>0.0</td><td>0.0</td><td>0.0</td><td>1.0</td></tr>
+ * </table>\endhtmlonly
+ *
+ * @param m The matrix to set.
+ * @param v The source matrix.
*/
extern void __attribute__((overloadable)) rsMatrixLoad(rs_matrix4x4 *m, const rs_matrix4x4 *v);
/**
* \overload
*/
extern void __attribute__((overloadable)) rsMatrixLoad(rs_matrix4x4 *m, const rs_matrix3x3 *v);
-
/**
- * Set the elements of a matrix from another matrix.
- *
- * @param m
+ * \overload
*/
extern void __attribute__((overloadable)) rsMatrixLoad(rs_matrix4x4 *m, const rs_matrix2x2 *v);
/**
@@ -124,11 +174,19 @@
/**
* Load a rotation matrix.
*
- * @param m
- * @param rot
- * @param x
- * @param y
- * @param z
+ * This function creates a rotation matrix. The axis of rotation is the
+ * <em>(x, y, z)</em> vector.
+ *
+ * To rotate a vector, multiply the vector by the created matrix
+ * using \ref rsMatrixMultiply.
+ *
+ * See http://en.wikipedia.org/wiki/Rotation_matrix .
+ *
+ * @param m The matrix to set.
+ * @param rot How much rotation to do, in degrees.
+ * @param x The x component of the vector that is the axis of rotation.
+ * @param y The y component of the vector that is the axis of rotation.
+ * @param z The z component of the vector that is the axis of rotation.
*/
extern void __attribute__((overloadable))
rsMatrixLoadRotate(rs_matrix4x4 *m, float rot, float x, float y, float z);
@@ -136,10 +194,16 @@
/**
* Load a scale matrix.
*
- * @param m
- * @param x
- * @param y
- * @param z
+ * This function creates a scaling matrix, where each component of a
+ * vector is multiplied by a number. This number can be negative.
+ *
+ * To scale a vector, multiply the vector by the created matrix
+ * using \ref rsMatrixMultiply.
+ *
+ * @param m The matrix to set.
+ * @param x The multiple to scale the x components by.
+ * @param y The multiple to scale the y components by.
+ * @param z The multiple to scale the z components by.
*/
extern void __attribute__((overloadable))
rsMatrixLoadScale(rs_matrix4x4 *m, float x, float y, float z);
@@ -147,20 +211,38 @@
/**
* Load a translation matrix.
*
- * @param m
- * @param x
- * @param y
- * @param z
+ * This function creates a translation matrix, where a
+ * number is added to each element of a vector.
+ *
+ * To translate a vector, multiply the vector by the created matrix
+ * using \ref rsMatrixMultiply.
+ *
+ * @param m The matrix to set.
+ * @param x The number to add to each x component.
+ * @param y The number to add to each y component.
+ * @param z The number to add to each z component.
*/
extern void __attribute__((overloadable))
rsMatrixLoadTranslate(rs_matrix4x4 *m, float x, float y, float z);
/**
- * Multiply two matrix (lhs, rhs) and place the result in m.
+ * Multiply two matrices.
*
- * @param m
- * @param lhs
- * @param rhs
+ * Sets \e m to the matrix product of <em>lhs * rhs</em>.
+ *
+ * To combine two 4x4 transformaton matrices, multiply the second transformation matrix
+ * by the first transformation matrix. E.g. to create a transformation matrix that applies
+ * the transformation \e s1 followed by \e s2, call
+ * </c>rsMatrixLoadMultiply(&combined, &s2, &s1)</c>.
+ *
+ * \warning Prior to version 21, storing the result back into right matrix is not supported and
+ * will result in undefined behavior. Use rsMatrixMulitply instead. E.g. instead of doing
+ * rsMatrixLoadMultiply (&m2r, &m2r, &m2l), use rsMatrixMultiply (&m2r, &m2l).
+ * rsMatrixLoadMultiply (&m2l, &m2r, &m2l) works as expected.
+ *
+ * @param m The matrix to set.
+ * @param lhs The left matrix of the product.
+ * @param rhs The right matrix of the product.
*/
extern void __attribute__((overloadable))
rsMatrixLoadMultiply(rs_matrix4x4 *m, const rs_matrix4x4 *lhs, const rs_matrix4x4 *rhs);
@@ -176,10 +258,16 @@
rsMatrixLoadMultiply(rs_matrix2x2 *m, const rs_matrix2x2 *lhs, const rs_matrix2x2 *rhs);
/**
- * Multiply the matrix m by rhs and place the result back into m.
+ * Multiply a matrix into another one.
*
- * @param m (lhs)
- * @param rhs
+ * Sets \e m to the matrix product <em>m * rhs</em>.
+ *
+ * When combining two 4x4 transformation matrices using this function, the resulting
+ * matrix will correspond to performing the \e rhs transformation first followed by
+ * the original \e m transformation.
+ *
+ * @param m The left matrix of the product and the matrix to be set.
+ * @param rhs The right matrix of the product.
*/
extern void __attribute__((overloadable))
rsMatrixMultiply(rs_matrix4x4 *m, const rs_matrix4x4 *rhs);
@@ -195,43 +283,73 @@
rsMatrixMultiply(rs_matrix2x2 *m, const rs_matrix2x2 *rhs);
/**
- * Multiple matrix m with a rotation matrix
+ * Multiply the matrix \e m with a rotation matrix.
*
- * @param m
- * @param rot
- * @param x
- * @param y
- * @param z
+ * This function modifies a transformation matrix to first do a rotation.
+ * The axis of rotation is the <em>(x, y, z)</em> vector.
+ *
+ * To apply this combined transformation to a vector, multiply
+ * the vector by the created matrix using \ref rsMatrixMultiply.
+ *
+ * @param m The matrix to modify.
+ * @param rot How much rotation to do, in degrees.
+ * @param x The x component of the vector that is the axis of rotation.
+ * @param y The y component of the vector that is the axis of rotation.
+ * @param z The z component of the vector that is the axis of rotation.
*/
extern void __attribute__((overloadable))
rsMatrixRotate(rs_matrix4x4 *m, float rot, float x, float y, float z);
/**
- * Multiple matrix m with a scale matrix
+ * Multiply the matrix \e m with a scaling matrix.
*
- * @param m
- * @param x
- * @param y
- * @param z
+ * This function modifies a transformation matrix to first do a scaling.
+ * When scaling, each component of a vector is multiplied by a number.
+ * This number can be negative.
+ *
+ * To apply this combined transformation to a vector, multiply
+ * the vector by the created matrix using \ref rsMatrixMultiply.
+ *
+ * @param m The matrix to modify.
+ * @param x The multiple to scale the x components by.
+ * @param y The multiple to scale the y components by.
+ * @param z The multiple to scale the z components by.
*/
extern void __attribute__((overloadable))
rsMatrixScale(rs_matrix4x4 *m, float x, float y, float z);
/**
- * Multiple matrix m with a translation matrix
+ * Multiply the matrix \e m with a translation matrix.
*
- * @param m
- * @param x
- * @param y
- * @param z
+ * This function modifies a transformation matrix to first
+ * do a translation. When translating, a number is added
+ * to each component of a vector.
+ *
+ * To apply this combined transformation to a vector, multiply
+ * the vector by the created matrix using \ref rsMatrixMultiply.
+ *
+ * @param m The matrix to modify.
+ * @param x The number to add to each x component.
+ * @param y The number to add to each y component.
+ * @param z The number to add to each z component.
*/
extern void __attribute__((overloadable))
rsMatrixTranslate(rs_matrix4x4 *m, float x, float y, float z);
/**
- * Load an Ortho projection matrix constructed from the 6 planes
+ * Load an orthographic projection matrix.
*
- * @param m
+ * Constructs an orthographic projection matrix, transforming the box
+ * identified by the six clipping planes <em>left, right, bottom, top,
+ * near, far</em> into a unit cube with a corner at
+ * <em>(-1, -1, -1)</em> and the opposite at <em>(1, 1, 1)</em>.
+ *
+ * To apply this projection to a vector, multiply the vector by the
+ * created matrix using \ref rsMatrixMultiply.
+ *
+ * See https://en.wikipedia.org/wiki/Orthographic_projection .
+ *
+ * @param m The matrix to set.
* @param left
* @param right
* @param bottom
@@ -243,9 +361,16 @@
rsMatrixLoadOrtho(rs_matrix4x4 *m, float left, float right, float bottom, float top, float near, float far);
/**
- * Load an Frustum projection matrix constructed from the 6 planes
+ * Load a frustum projection matrix.
*
- * @param m
+ * Constructs a frustum projection matrix, transforming the box
+ * identified by the six clipping planes <em>left, right, bottom, top,
+ * near, far</em>.
+ *
+ * To apply this projection to a vector, multiply the vector by the
+ * created matrix using \ref rsMatrixMultiply.
+ *
+ * @param m The matrix to set.
* @param left
* @param right
* @param bottom
@@ -257,21 +382,36 @@
rsMatrixLoadFrustum(rs_matrix4x4 *m, float left, float right, float bottom, float top, float near, float far);
/**
- * Load an perspective projection matrix constructed from the 6 planes
+ * Load a perspective projection matrix.
*
- * @param m
+ * Constructs a perspective projection matrix, assuming a symmetrical field of view.
+ *
+ * To apply this projection to a vector, multiply the vector by the
+ * created matrix using \ref rsMatrixMultiply.
+ *
+ * @param m The matrix to set.
* @param fovy Field of view, in degrees along the Y axis.
* @param aspect Ratio of x / y.
- * @param near
- * @param far
+ * @param near The near clipping plane.
+ * @param far The far clipping plane.
*/
extern void __attribute__((overloadable))
rsMatrixLoadPerspective(rs_matrix4x4* m, float fovy, float aspect, float near, float far);
#if !defined(RS_VERSION) || (RS_VERSION < 14)
/**
- * Multiply a vector by a matrix and return the result vector.
- * API version 10-13
+ * Multiply a vector by a matrix.
+ *
+ * Returns the post-multiplication of the vector by the matrix, ie. <em>m * in</em>.
+ *
+ * When multiplying a \e float3 to a \e rs_matrix4x4, the vector is expanded with (1).
+ *
+ * When multiplying a \e float2 to a \e rs_matrix4x4, the vector is expanded with (0, 1).
+ *
+ * When multiplying a \e float2 to a \e rs_matrix3x3, the vector is expanded with (0).
+ *
+ * This function is available in API version 10-13. Starting with API 14,
+ * the function takes a const matrix as the first argument.
*/
_RS_RUNTIME float4 __attribute__((overloadable))
rsMatrixMultiply(rs_matrix4x4 *m, float4 in);
@@ -307,8 +447,17 @@
rsMatrixMultiply(rs_matrix2x2 *m, float2 in);
#else
/**
- * Multiply a vector by a matrix and return the result vector.
- * API version 14+
+ * Multiply a vector by a matrix.
+ *
+ * Returns the post-multiplication of the vector of the matrix, i.e. <em>m * in</em>.
+ *
+ * When multiplying a \e float3 to a \e rs_matrix4x4, the vector is expanded with (1).
+ *
+ * When multiplying a \e float2 to a \e rs_matrix4x4, the vector is expanded with (0, 1).
+ *
+ * When multiplying a \e float2 to a \e rs_matrix3x3, the vector is expanded with (0).
+ *
+ * This function is available starting with API version 14.
*/
_RS_RUNTIME float4 __attribute__((overloadable))
rsMatrixMultiply(const rs_matrix4x4 *m, float4 in);
@@ -346,23 +495,28 @@
/**
- * Returns true if the matrix was successfully inversed
+ * Inverts a matrix in place.
*
- * @param m
+ * Returns true if the matrix was successfully inverted.
+ *
+ * @param m The matrix to invert.
*/
extern bool __attribute__((overloadable)) rsMatrixInverse(rs_matrix4x4 *m);
/**
- * Returns true if the matrix was successfully inversed and transposed.
+ * Inverts and transpose a matrix in place.
*
- * @param m
+ * The matrix is first inverted then transposed.
+ * Returns true if the matrix was successfully inverted.
+ *
+ * @param m The matrix to modify.
*/
extern bool __attribute__((overloadable)) rsMatrixInverseTranspose(rs_matrix4x4 *m);
/**
- * Transpose the matrix m.
+ * Transpose the matrix m in place.
*
- * @param m
+ * @param m The matrix to transpose.
*/
extern void __attribute__((overloadable)) rsMatrixTranspose(rs_matrix4x4 *m);
/**