1 files changed, 107 insertions, 0 deletions
diff --git a/sdl/glframe.c b/sdl/glframe.c
new file mode 100644
index 0000000..fa6b461
--- /dev/null
+++ b/sdl/glframe.c
@@ -0,0 +1,107 @@
+/* glframe.c
+ *
+ * Camera
+ *
+ * note: we could make these functions to be inlines, but they would need
+ * to be moved into the header
+ *
+ */
+
+#include "glframe.h"
+#include "math3d.h"
+
+void reset_glframe(GLFrame *frame)
+{
+	frame->v_location[0] = 0.0f;
+	frame->v_location[1] = 0.0f;
+	frame->v_location[2] = 0.0f;
+	
+	frame->v_forward[0] = 0.0f;
+	frame->v_forward[1] = 0.0f;
+	frame->v_forward[2] = -1.0f;
+	
+	frame->v_up[0] = 0.0f;
+	frame->v_up[1] = 1.0f;
+	frame->v_up[2] = 0.0f;
+}
+
+/* get a 4x4 transformation matrix that describes the ccamera orientation */
+void get_camera_orientation(GLFrame *frame, M3DMatrix44f m)
+{
+    M3DVector3f x, z;
+
+    /* make rotation matrix, z vector is reversed */
+    z[0] = -frame->v_forward[0];
+    z[1] = -frame->v_forward[1];
+    z[2] = -frame->v_forward[2];
+
+    /* x vector = y cross z */ 
+    m3dCrossProductf(x, frame->v_up, z);
+
+    /* matrix has no translation information and is transposed */
+    #define M(row,col)  m[col*4+row]
+    M(0, 0) = x[0];
+    M(0, 1) = x[1];
+    M(0, 2) = x[2];
+    M(0, 3) = 0.0;
+    M(1, 0) = frame->v_up[0];
+    M(1, 1) = frame->v_up[1];
+    M(1, 2) = frame->v_up[2];
+    M(1, 3) = 0.0;
+    M(2, 0) = z[0];
+    M(2, 1) = z[1];
+    M(2, 2) = z[2];
+    M(2, 3) = 0.0;
+    M(3, 0) = 0.0;
+    M(3, 1) = 0.0;
+    M(3, 2) = 0.0;
+    M(3, 3) = 1.0;
+    #undef M 
+}
+
+/* perform viewing or modeling transformations */
+/* some of the code is unimplemented */     
+void apply_camera_transform(GLFrame *frame)    
+{
+    M3DMatrix44f m;
+    get_camera_orientation(frame, m);  
+    glMultMatrixf(m);
+
+#if 0
+    /* if Rotation only, then do not do the translation */
+    if (!rot_only)
+        glTranslatef(-v_location[0], -v_location[1], -v_location[2]);
+
+    gluLookAt(v_location[0], v_location[1], v_location[2],
+                v_location[0] + v_forward[0], 
+                v_location[1] + v_forward[1], 
+                v_location[2] + v_forward[2], 
+                v_up[0], v_up[1], v_up[2]);
+#endif                
+}
+
+void move_forward(GLFrame *frame, float delta)
+{
+    // Move along direction of front direction
+    frame->v_location[0] += frame->v_forward[0] * delta;
+    frame->v_location[1] += frame->v_forward[1] * delta;
+    frame->v_location[2] += frame->v_forward[2] * delta;
+}
+
+void rotate_local_y(GLFrame *frame, float angle)
+{
+    M3DMatrix44f rotMat;
+
+    /* just Rotate around the up vector */
+    /* create a rotation matrix around my Up (Y) vector */
+    m3dRotationMatrix44f(rotMat, angle, frame->v_up[0], frame->v_up[1], frame->v_up[2]);
+
+    M3DVector3f newVect;
+
+    /* rotate forward pointing vector (inlined 3x3 transform) */
+    newVect[0] = rotMat[0] * frame->v_forward[0] + rotMat[4] * frame->v_forward[1] + rotMat[8] *  frame->v_forward[2];    
+    newVect[1] = rotMat[1] * frame->v_forward[0] + rotMat[5] * frame->v_forward[1] + rotMat[9] *  frame->v_forward[2];    
+    newVect[2] = rotMat[2] * frame->v_forward[0] + rotMat[6] * frame->v_forward[1] + rotMat[10] * frame->v_forward[2];    
+    m3dCopyVector3f(frame->v_forward, newVect);
+}
+