opengl_learn

commit 0e6c9099c9414a8108e85d9228aac2d96907ba79
parent 580f490d75b1d4cd9ce697e03b851a5030010f0c
Author: David DiPaola <DavidDiPaola@users.noreply.github.com>
Date:   Sat,  6 Oct 2018 09:09:44 -0400

05: added rotation transformation

Diffstat:
M
05-geometrytransforms.c
 | 
4
++--
M
ogl/Makefile
 | 
2
+-
M
ogl/ogl.h
 | 
11
+++++++++++
A
ogl/ogl_mat4f_rotate.c
 | 
34
++++++++++++++++++++++++++++++++++

4 files changed, 48 insertions(+), 3 deletions(-)
diff --git a/05-geometrytransforms.c b/05-geometrytransforms.c
@@ -88,11 +88,11 @@ main() {
 
 	struct ogl_mat4f MVP_model;
 	struct ogl_vec3f MVP_model_translation = { .x= 0.0f,  .y= 0.0f,  .z=-1.0f };
-	/* TODO model rotation */
+	struct ogl_quat  MVP_model_rotation    = { .angle= 3.14f/3.0f, .axis={ .x= 0.0f, .y= 1.0f, .z= 0.0f } };
 	struct ogl_vec3f MVP_model_scale       = { .x= 2.0f,  .y= 2.0f,  .z= 2.0f };
 	ogl_mat4f_identity( &MVP_model);
 	ogl_mat4f_translate(MVP_model, MVP_model_translation, &MVP_model);
-	/* TODO model rotation */
+	ogl_mat4f_rotate(   MVP_model, MVP_model_rotation,    &MVP_model);
 	ogl_mat4f_scale(    MVP_model, MVP_model_scale,       &MVP_model);
 
 	struct ogl_mat4f MVP;
diff --git a/ogl/Makefile b/ogl/Makefile
@@ -1,7 +1,7 @@
 SRC = \
 	_ogl.c ogl_init.c \
 	ogl_GLfloat_isapproxequal.c ogl_GLfloat_print.c \
-	ogl_mat4f_identity.c ogl_mat4f_isapproxequal.c ogl_mat4f_multiply.c ogl_mat4f_print.c ogl_mat4f_scale.c ogl_mat4f_translate.c \
+	ogl_mat4f_identity.c ogl_mat4f_isapproxequal.c ogl_mat4f_multiply.c ogl_mat4f_print.c ogl_mat4f_rotate.c ogl_mat4f_scale.c ogl_mat4f_translate.c \
 	ogl_program_build.c ogl_program_uniform_get_ID.c ogl_program_uniform_set_mat4f.c \
 	ogl_vec3f_cross.c ogl_vec3f_dot.c ogl_vec3f_isapproxequal.c ogl_vec3f_magnitude.c ogl_vec3f_normal.c ogl_vec3f_print.c \
 	ogl_arraybuffer_load.c \
diff --git a/ogl/ogl.h b/ogl/ogl.h
@@ -22,6 +22,11 @@ struct ogl_vec3f {
 	GLfloat z;
 };
 
+struct ogl_quat {
+	GLfloat angle;
+	struct ogl_vec3f axis;
+};
+
 
 
 GLFWwindow *
@@ -84,6 +89,12 @@ ogl_mat4f_print(
 );
 
 void
+ogl_mat4f_rotate(
+	struct ogl_mat4f matrix, struct ogl_quat rotation,
+	struct ogl_mat4f * out_result
+);
+
+void
 ogl_mat4f_scale(
 	struct ogl_mat4f matrix, struct ogl_vec3f scale,
 	struct ogl_mat4f * out_result
diff --git a/ogl/ogl_mat4f_rotate.c b/ogl/ogl_mat4f_rotate.c
@@ -0,0 +1,34 @@
+/*
+2018 David DiPaola
+licensed under CC0 (public domain, see https://creativecommons.org/publicdomain/zero/1.0/)
+*/
+
+#define _ISOC99_SOURCE
+#include <math.h>
+
+#include "ogl.h"
+
+void
+ogl_mat4f_rotate(
+	struct ogl_mat4f matrix, struct ogl_quat rotation,
+	struct ogl_mat4f * out_result
+) {
+	/* see OpenGL 2.1 glRotate(): https://www.khronos.org/registry/OpenGL-Refpages/gl2.1/xhtml/glRotate.xml */
+	/* note: glRotate() was deprecated, then removed from later OpenGL versions. don't use it */
+
+	struct ogl_vec3f axis;
+	ogl_vec3f_normal(rotation.axis, &axis);
+	GLfloat x = rotation.axis.x;
+	GLfloat y = rotation.axis.y;
+	GLfloat z = rotation.axis.z;
+	GLfloat c = cosf(rotation.angle);
+	GLfloat s = sinf(rotation.angle);
+	struct ogl_mat4f rotation_matrix = { .values = {
+		(x*x*(1-c))+(  c), (x*y*(1-c))-(z*s), (x*z*(1-c))+(y*s), 0.0f,
+		(y*x*(1-c))+(z*s), (y*y*(1-c))+(  c), (y*z*(1-c))-(x*s), 0.0f,
+		(x*z*(1-c))-(y*s), (y*z*(1-c))+(x*s), (z*z*(1-c))+(  c), 0.0f,
+		             0.0f,              0.0f,              0.0f, 1.0f,
+	}};
+	ogl_mat4f_multiply(matrix, rotation_matrix, out_result);
+}
+