maintenance and added vec3Set

src/matrix-math.c

@@ -30,7 +30,7 @@ void mat4Empty(mat4 mat) {
 }
 
 /**
- * mutliplies A with B and stores the result in results
+ * mutliplies A with B and stores the result in result
  */
 void mat4Multiply(mat4 result, mat4 A, mat4 B) {
 	// if result is one of the arguments, modify copy instead of result directly
@@ -41,13 +41,19 @@ void mat4Multiply(mat4 result, mat4 A, mat4 B) {
 		return;
 	}
 
+	// loops over cells of the result matrix
 	for (int i = 0; i < 16; i++) {
 		int col = i / 4;
 		int row = i % 4;
+
+		// pointer to the current cell
 		GLfloat* curr = &(result[i]);
 
+		// initialise current cell with 0
 		*curr = 0;
 
+		// loop over the row of A and column of B
+		// continuously adding the multiplication of the two values to the result cell
 		for (int j = 0; j < 4; j++) {
 			*curr += A[row + j * 4] * B[j + col * 4];
 		}
@@ -66,6 +72,9 @@ void mat4Print(mat4 m) {
 	}
 }
 
+/**
+ * translates by the vector v
+ */
 void mat4Translate(mat4 out, mat4 in, vec3 v) {
 	mat4 T;
 	mat4Identity(T);
@@ -77,6 +86,9 @@ void mat4Translate(mat4 out, mat4 in, vec3 v) {
 	mat4Multiply(out, T, in);
 }
 
+/**
+ * scales by the vector v
+ */
 void mat4Scale(mat4 out, mat4 in, vec3 v) {
 	mat4 T;
 	mat4Identity(T);
@@ -88,6 +100,10 @@ void mat4Scale(mat4 out, mat4 in, vec3 v) {
 	mat4Multiply(out, T, in);
 }
 
+
+/**
+ * rotates around the X axis by the angle a (in radians)
+ */
 void mat4RotateX(mat4 out, mat4 in, GLfloat a) {
 	mat4 T;
 	mat4Identity(T);
@@ -100,6 +116,9 @@ void mat4RotateX(mat4 out, mat4 in, GLfloat a) {
 	mat4Multiply(out, T, in);
 }
 
+/**
+ * rotates around the Y axis by the angle a (in radians)
+ */
 void mat4RotateY(mat4 out, mat4 in, GLfloat a) {
 	mat4 T;
 	mat4Identity(T);
@@ -112,6 +131,9 @@ void mat4RotateY(mat4 out, mat4 in, GLfloat a) {
 	mat4Multiply(out, T, in);
 }
 
+/**
+ * rotates around the Z axis by the angle a (in radians)
+ */
 void mat4RotateZ(mat4 out, mat4 in, GLfloat a) {
 	mat4 T;
 	mat4Identity(T);
@@ -124,38 +146,12 @@ void mat4RotateZ(mat4 out, mat4 in, GLfloat a) {
 	mat4Multiply(out, T, in);
 }
 
-void vec3Subtract(vec3 out, vec3 a, vec3 b) {
+/**
-	out[0] = a[0] - b[0];
+ * builds a look-at matrix, overwriting out
-	out[1] = a[1] - b[1];
+ * eye is the position of the camera
-	out[2] = a[2] - b[2];
+ * look is the position of the target to be looked at
-}
+ * up is the up vector
-
+ */
-void vec3CrossProduct(vec3 out, vec3 a, vec3 b) {
-	vec3 result;
-	result[0] = a[1] * b[2] - a[2] * b[1];
-	result[1] = a[2] * b[0] - a[0] * b[2];
-	result[2] = a[0] * b[1] - a[1] * b[0];
-
-	out[0] = result[0];
-	out[1] = result[1];
-	out[2] = result[2];
-}
-
-void vec3Normalise(vec3 out, vec3 in) {
-	GLfloat length = vec3Length(in);
-	out[0] = in[0] / length;
-	out[1] = in[1] / length;
-	out[2] = in[2] / length;
-}
-
-GLfloat vec3Length(vec3 in) {
-	return sqrt(in[0] * in[0] + in[1] * in[1] + in[2] * in[2]);
-}
-
-GLfloat vec3DotProduct(vec3 a, vec3 b) {
-	return a[0] * b[0] + a[1] * b[1] + a[2] * b[2];
-}
-
 void mat4BuildLookAt(mat4 out, vec3 eye, vec3 look, vec3 up) {
 	vec3 n;
 	vec3 u;
@@ -182,6 +178,11 @@ void mat4BuildLookAt(mat4 out, vec3 eye, vec3 look, vec3 up) {
 	out[3] = 0;    out[7] = 0;    out[11] = 0;    out[15] = 1;
 }
 
+/**
+ * builds a projection matrix, overwriting out
+ * r, l, t, b are the right, left, top and bottom of the frustum
+ * n and f are the distance of the near and far planes from the camera
+ */
 void mat4BuildProjection(mat4 out, GLfloat r, GLfloat l, GLfloat t, GLfloat b, GLfloat n, GLfloat f) {
 	mat4Identity(out);
 
@@ -196,6 +197,12 @@ void mat4BuildProjection(mat4 out, GLfloat r, GLfloat l, GLfloat t, GLfloat b, G
 	out[14] = - 2.0f * f / (f - n);
 }
 
+/**
+ * builds a perspective projection matrix, overwriting out
+ * fovy is the field of view in the y direction
+ * aspect is the aspect ratio
+ * n and f are the distance of the near and far planes from the camera
+ */
 void mat4BuildPerspective(mat4 out, GLfloat fovy, GLfloat aspect, GLfloat n, GLfloat f) {
 	GLfloat t = n * tan(0.5f * fovy);
 	GLfloat b = -t;
@@ -205,3 +212,60 @@ void mat4BuildPerspective(mat4 out, GLfloat fovy, GLfloat aspect, GLfloat n, GLf
 
 	mat4BuildProjection(out, r, l, t, b, n, f);
 }
+
+
+/**
+ * subtracts b from a, storing the result in out
+ */
+void vec3Subtract(vec3 out, vec3 a, vec3 b) {
+	out[0] = a[0] - b[0];
+	out[1] = a[1] - b[1];
+	out[2] = a[2] - b[2];
+}
+
+/**
+ * calculates the cross product of a and b, storing the result in out
+ */
+void vec3CrossProduct(vec3 out, vec3 a, vec3 b) {
+	vec3 result;
+	result[0] = a[1] * b[2] - a[2] * b[1];
+	result[1] = a[2] * b[0] - a[0] * b[2];
+	result[2] = a[0] * b[1] - a[1] * b[0];
+
+	out[0] = result[0];
+	out[1] = result[1];
+	out[2] = result[2];
+}
+
+/**
+ * normalizes in storing the result in out
+ */
+void vec3Normalise(vec3 out, vec3 in) {
+	GLfloat length = vec3Length(in);
+	out[0] = in[0] / length;
+	out[1] = in[1] / length;
+	out[2] = in[2] / length;
+}
+
+/**
+ * returns the length of the vector in
+ */
+GLfloat vec3Length(vec3 in) {
+	return sqrt(in[0] * in[0] + in[1] * in[1] + in[2] * in[2]);
+}
+
+/**
+ * returns the dot product of the vectors a and b
+ */
+GLfloat vec3DotProduct(vec3 a, vec3 b) {
+	return a[0] * b[0] + a[1] * b[1] + a[2] * b[2];
+}
+
+/**
+ * sets the values of out to x, y and z
+ */
+void vec3Set(vec3 out, GLfloat x, GLfloat y, GLfloat z) {
+	out[0] = x;
+	out[1] = y;
+	out[2] = z;
+}

src/matrix-math.h

@@ -31,5 +31,6 @@ extern void vec3CrossProduct(vec3 out, vec3 a, vec3 b);
 extern void vec3Normalise(vec3 out, vec3 in);
 extern GLfloat vec3Length(vec3 in);
 extern GLfloat vec3DotProduct(vec3 a, vec3 b);
+extern void vec3Set(vec3 out, GLfloat x, GLfloat y, GLfloat z);
 
 #endif