add _scale_as feature

glm_vec_scale multiplies vector (all items) by a scalar
result = vector * factor, new scale = old scale * factor

now it is possible to scale a vector as specified factor
result = unit(vector) * factor, new scale = factor

include/call/cglmc-vec.h

@@ -94,6 +94,18 @@ CGLM_EXPORT
 void
 glmc_vec_scale(vec3 v, float s, vec3 dest);
 
+CGLM_EXPORT
+void
+glmc_vec4_scale(vec4 v, float s, vec4 dest);
+
+CGLM_EXPORT
+void
+glmc_vec_scale_as(vec3 v, float s, vec3 dest);
+
+CGLM_EXPORT
+void
+glmc_vec4_scale_as(vec3 v, float s, vec3 dest);
+
 CGLM_EXPORT
 void
 glmc_vec_flipsign(vec3 v);
@@ -102,10 +114,6 @@ CGLM_EXPORT
 void
 glmc_vec4_flipsign(vec4 v);
 
-CGLM_EXPORT
-void
-glmc_vec4_scale(vec4 v, float s, vec4 dest);
-
 CGLM_EXPORT
 float
 glmc_vec_angle(vec3 v1, vec3 v2)

include/cglm-vec.h

@@ -249,7 +249,7 @@ glm_vec4_sub(vec4 v1, vec4 v2, vec4 dest) {
 }
 
 /*!
- * @brief multiply vec3 vector with scalar
+ * @brief multiply/scale vec3 vector with scalar: result = v * s
  *
  * @param[in]  v    vector
  * @param[in]  s    scalar
@@ -263,6 +263,70 @@ glm_vec_scale(vec3 v, float s, vec3 dest) {
   dest[2] = v[2] * s;
 }
 
+/*!
+ * @brief multiply/scale vec4 vector with scalar: result = v * s
+ *
+ * @param[in]  v    vector
+ * @param[in]  s    scalar
+ * @param[out] dest destination vector
+ */
+CGLM_INLINE
+void
+glm_vec4_scale(vec4 v, float s, vec4 dest) {
+#if defined( __SSE__ ) || defined( __SSE2__ )
+  _mm_store_ps(dest,
+               _mm_mul_ps(_mm_load_ps(v),
+                          _mm_set1_ps(s)));
+#else
+  dest[0] = v[0] * s;
+  dest[1] = v[1] * s;
+  dest[2] = v[2] * s;
+  dest[3] = v[3] * s;
+#endif
+}
+
+/*!
+ * @brief make vec3 vector scale as specified: result = unit(v) * s
+ *
+ * @param[in]  v    vector
+ * @param[in]  s    scalar
+ * @param[out] dest destination vector
+ */
+CGLM_INLINE
+void
+glm_vec_scale_as(vec3 v, float s, vec3 dest) {
+  float norm;
+  norm = glm_vec_norm(v);
+
+  if (norm == 0) {
+    glm_vec_copy(v, dest);
+    return;
+  }
+
+  glm_vec_scale(v, s / norm, dest);
+}
+
+/*!
+ * @brief make vec4 vector scale as specified: result = unit(v) * s
+ *
+ * @param[in]  v    vector
+ * @param[in]  s    scalar
+ * @param[out] dest destination vector
+ */
+CGLM_INLINE
+void
+glm_vec4_scale_as(vec4 v, float s, vec4 dest) {
+  float norm;
+  norm = glm_vec4_norm(v);
+
+  if (norm == 0) {
+    glm_vec4_copy(v, dest);
+    return;
+  }
+
+  glm_vec4_scale(v, s / norm, dest);
+}
+
 /*!
  * @brief flip sign of all vec3 members
  *
@@ -299,28 +363,6 @@ glm_vec4_flipsign(vec4 v) {
 #endif
 }
 
-/*!
- * @brief multiply vec4 vector with scalar
- *
- * @param[in]  v    vector
- * @param[in]  s    scalar
- * @param[out] dest destination vector
- */
-CGLM_INLINE
-void
-glm_vec4_scale(vec4 v, float s, vec4 dest) {
-#if defined( __SSE__ ) || defined( __SSE2__ )
-  _mm_store_ps(dest,
-               _mm_mul_ps(_mm_load_ps(v),
-                          _mm_set1_ps(s)));
-#else
-  dest[0] = v[0] * s;
-  dest[1] = v[1] * s;
-  dest[2] = v[2] * s;
-  dest[3] = v[3] * s;
-#endif
-}
-
 /*!
  * @brief normalize vec3 and store result in same vec
  *

src/cglm-vec.c

@@ -121,6 +121,24 @@ glmc_vec_scale(vec3 v, float s, vec3 dest) {
   glm_vec_scale(v, s, dest);
 }
 
+CGLM_EXPORT
+void
+glmc_vec4_scale(vec4 v, float s, vec4 dest) {
+  glm_vec4_scale(v, s, dest);
+}
+
+CGLM_EXPORT
+void
+glmc_vec_scale_as(vec3 v, float s, vec3 dest) {
+  glm_vec_scale_as(v, s, dest);
+}
+
+CGLM_EXPORT
+void
+glmc_vec4_scale_as(vec3 v, float s, vec3 dest) {
+  glm_vec4_scale_as(v, s, dest);
+}
+
 CGLM_EXPORT
 void
 glmc_vec_flipsign(vec3 v) {
@@ -133,12 +151,6 @@ glmc_vec4_flipsign(vec4 v) {
   glm_vec4_flipsign(v);
 }
 
-CGLM_EXPORT
-void
-glmc_vec4_scale(vec4 v, float s, vec4 dest) {
-  glm_vec4_scale(v, s, dest);
-}
-
 CGLM_EXPORT
 float
 glmc_vec_angle(vec3 v1, vec3 v2) {