Fix FloatUtil.makePerspective(..): The tan(fovy/2) shall be used, not tan(fovy), fix callers; Simplify FloatUtil.makePerspective(..FovHVHalves..)

Fix FloatUtil.makePerspective(..): The tan(fovy/2) shall be used, not tan(fovy), fix callers
 - This bug didn't hit (yet), since callers already performed the division (degree -> radian)
   by falsly claiming the passed value is in radian - where it was actually fov/2 in radians.

Simplify FloatUtil.makePerspective(..FovHVHalves..)
 - Due to the fix above, it became pretty clear that the makeFrustum(..)
   method can be utilized.
   Simply apply all our tan-half-fov values on zNear.

2 files changed, 47 insertions, 57 deletions

diff --git a/src/jogl/classes/com/jogamp/opengl/math/FloatUtil.java b/src/jogl/classes/com/jogamp/opengl/math/FloatUtil.java
index 3c6a867e6..d2e535eaf 100644
--- a/src/jogl/classes/com/jogamp/opengl/math/FloatUtil.java
+++ b/src/jogl/classes/com/jogamp/opengl/math/FloatUtil.java
@@ -558,18 +558,18 @@ public final class FloatUtil {
    * @param m_offset offset in given array <i>m</i>, i.e. start of the 4x4 matrix
    * @param initM if true, given matrix will be initialized w/ identity matrix,
    *              otherwise only the frustum fields are set.
-   * @param fovy angle in radians
+   * @param fovy_rad angle in radians
    * @param aspect
    * @param zNear
    * @param zFar
    * @return given matrix for chaining
    */
   public static float[] makePerspective(final float[] m, final int m_off, final boolean initM,
-                                        final float fovy, final float aspect, final float zNear, final float zFar) {
-      final float top=(float)Math.tan(fovy)*zNear;
-      final float bottom=-1.0f*top;
-      final float left=aspect*bottom;
-      final float right=aspect*top;
+                                        final float fovy_rad, final float aspect, final float zNear, final float zFar) {
+      final float top    =  tan(fovy_rad/2f) * zNear; // use tangent of half-fov !
+      final float bottom =  -1.0f * top;
+      final float left   = aspect * bottom;
+      final float right  = aspect * top;
       return makeFrustum(m, m_off, initM, left, right, bottom, top, zNear, zFar);
   }
 
@@ -591,53 +591,12 @@ public final class FloatUtil {
    */
   public static float[] makePerspective(final float[] m, final int m_offset, final boolean initM,
                                         final FovHVHalves fovhv, final float zNear, final float zFar) {
-      if( initM ) {
-          // m[m_offset+0+4*0] = 1f;
-          m[m_offset+1+4*0] = 0f;
-          m[m_offset+2+4*0] = 0f;
-          m[m_offset+3+4*0] = 0f;
-
-          m[m_offset+0+4*1] = 0f;
-          // m[m_offset+1+4*1] = 1f;
-          m[m_offset+2+4*1] = 0f;
-          m[m_offset+3+4*1] = 0f;
-
-          // m[m_offset+0+4*2] = 0f;
-          // m[m_offset+1+4*2] = 0f;
-          // m[m_offset+2+4*2] = 1f;
-          // m[m_offset+3+4*2] = 0f;
-
-          m[m_offset+0+4*3] = 0f;
-          m[m_offset+1+4*3] = 0f;
-          // m[m_offset+2+4*3] = 0f;
-          // m[m_offset+3+4*3] = 1f;
-      }
-
-      final float projScaleX  = 2.0f / ( fovhv.left + fovhv.right  );
-      final float projScaleY  = 2.0f / ( fovhv.top  + fovhv.bottom );
-      final float projOffsetX =       ( fovhv.left - fovhv.right  ) * projScaleX * 0.5f;
-      final float projOffsetY = -1f * ( fovhv.top  - fovhv.bottom ) * projScaleY * 0.5f;
-
-      // Produces X result, mapping clip edges to [-w,+w]
-      m[m_offset+0+4*0] = projScaleX;
-      m[m_offset+0+4*2] = -1f * projOffsetX;
-
-      // Produces Y result, mapping clip edges to [-w,+w] (Y=up)
-      m[m_offset+1+4*1] = projScaleY;
-      m[m_offset+1+4*2] = -1f * projOffsetY;
-
-      // Custom Z-buffer result .. same as frustum matrix!
-      m[m_offset+2+4*2] = -1.0f*(zFar+zNear)/(zFar-zNear);
-      m[m_offset+2+4*3] = -2.0f*(zFar*zNear)/(zFar-zNear);
-      // alternative:
-      // m[m_offset+2+4*2] = -1.0f * zFar / (zNear - zFar);
-      // m[m_offset+2+4*3] = (zFar * zNear) / (zNear - zFar);
-
-      // Produces W result (= Z in)
-      m[m_offset+3+4*2] = -1.0f;
-      m[m_offset+3+4*3] = 0f;
-
-      return m;
+      final FovHVHalves fovhvTan = fovhv.getInTangents();  // use tangent of half-fov !
+      final float top    =         fovhvTan.top    * zNear;
+      final float bottom = -1.0f * fovhvTan.bottom * zNear;
+      final float left   = -1.0f * fovhvTan.left   * zNear;
+      final float right  =         fovhvTan.right  * zNear;
+      return makeFrustum(m, m_offset, initM, left, right, bottom, top, zNear, zFar);
   }
 
   /**
diff --git a/src/jogl/classes/com/jogamp/opengl/math/FovHVHalves.java b/src/jogl/classes/com/jogamp/opengl/math/FovHVHalves.java
index 18bba8c45..786d146e6 100644
--- a/src/jogl/classes/com/jogamp/opengl/math/FovHVHalves.java
+++ b/src/jogl/classes/com/jogamp/opengl/math/FovHVHalves.java
@@ -48,7 +48,10 @@ public final class FovHVHalves {
 
     /**
      * Constructor for one {@link FovHVHalves} instance.
-     *
+     * <p>
+     * It is recommended to pass and store values in tangent
+     * if used for perspective FOV calculations, since it will avoid conversion to tangent later on.
+     * </p>
      * @param left half horizontal FOV, left side, in tangent or radians
      * @param right half horizontal FOV, right side, in tangent or radians
      * @param top half vertical FOV, top side, in tangent or radians
@@ -73,11 +76,26 @@ public final class FovHVHalves {
      * @param verticalFov whole vertical FOV in radians
      */
     public static FovHVHalves createByRadians(final float horizontalFov, final float verticalFov) {
-        final float halfHorizFovTan = (float)Math.tan(horizontalFov/2f);
-        final float halfVertFovTan = (float)Math.tan(verticalFov/2f);
+        final float halfHorizFovTan = FloatUtil.tan(horizontalFov/2f);
+        final float halfVertFovTan = FloatUtil.tan(verticalFov/2f);
         return new FovHVHalves(halfHorizFovTan, halfHorizFovTan, halfVertFovTan, halfVertFovTan, true);
     }
 
+    /**
+     * Returns this instance values <i>in tangent</i> values.
+     * <p>
+     * If this instance is {@link #inTangents} already, method returns this instance,
+     * otherwise a newly created instance w/ converted values to tangent.
+     * </p>
+     */
+    public final FovHVHalves getInTangents() {
+        if( inTangents ) {
+            return this;
+        } else {
+            return new FovHVHalves(FloatUtil.tan(left), FloatUtil.tan(right), FloatUtil.tan(top), FloatUtil.tan(bottom), true);
+        }
+    }
+
     /** Returns the full horizontal FOV, i.e. {@link #left} + {@link #right}. */
     public final float horzFov() { return left+right; }
 
@@ -85,6 +103,19 @@ public final class FovHVHalves {
     public final float vertFov() { return top+bottom; }
 
     public final String toString() {
-        return "FovHVHalves["+(inTangents?"tangents":"radians")+": "+left+" l, "+right+" r, "+top+" t, "+bottom+" b]";
+        return "FovHVH["+(inTangents?"tangents":"radians")+": "+left+" l, "+right+" r, "+top+" t, "+bottom+" b]";
+    }
+    public final String toStringInDegrees() {
+        final float f = 180.0f / FloatUtil.PI;
+        final String storedAs = inTangents?"tangents":"radians";
+        if( inTangents ) {
+            final float aleft = FloatUtil.atan(left);
+            final float aright = FloatUtil.atan(right);
+            final float atop = FloatUtil.atan(top);
+            final float abottom = FloatUtil.atan(bottom);
+            return "FovHVH[degrees: "+aleft*f+" l, "+aright*f+" r, "+atop*f+" t, "+abottom*f+" b, stored-as: "+storedAs+"]";
+        } else {
+            return "FovHVH[degrees: "+left*f+" l, "+right*f+" r, "+top*f+" t, "+bottom*f+" b, stored-as: "+storedAs+"]";
+        }
     }
 }