From 86adbefc018c98ff18d7c4f6f52d97b53f3537fc Mon Sep 17 00:00:00 2001
From: =?utf8?q?Alexis=20Laferri=C3=A8re?= <alexis.laf@xymus.net>
Date: Tue, 19 Jan 2016 12:26:58 -0500
Subject: [PATCH] lib/gamnit depth: add stereoscopic view module
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Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
---
 lib/gamnit/depth/stereoscopic_view.nit |   88 ++++++++++++++++++++++++++++++++
 1 file changed, 88 insertions(+)
 create mode 100644 lib/gamnit/depth/stereoscopic_view.nit

diff --git a/lib/gamnit/depth/stereoscopic_view.nit b/lib/gamnit/depth/stereoscopic_view.nit
new file mode 100644
index 0000000..2857e7d
--- /dev/null
+++ b/lib/gamnit/depth/stereoscopic_view.nit
@@ -0,0 +1,88 @@
+# This file is part of NIT ( http://www.nitlanguage.org ).
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Refine `EulerCamera` and `App::frame_core_draw` to get a stereoscopic view
+module stereoscopic_view
+
+import depth
+intrude import cameras
+
+redef class EulerCamera
+	redef var mvp_matrix = new Matrix.identity(4)
+
+	# Half of the distance between the eyes
+	var eye_separation: Float = 0.03125
+
+	# MVP matrix for the left eye
+	fun mvp_matrix_left: Matrix do return mvp_matrix_eye(eye_separation)
+
+	# MVP matrix for the right eye
+	fun mvp_matrix_right: Matrix do return mvp_matrix_eye(-eye_separation)
+
+	# Get an MVP matrix for an eye at `diff` world unit from the center
+	private fun mvp_matrix_eye(diff: Float): Matrix
+	do
+		var view = new Matrix.identity(4)
+
+		# Translate the world away from the camera
+		view.translate(-position.x/2.0, -position.y/2.0, -position.z/2.0)
+
+		# Rotate the camera, first by looking left or right, then up or down
+		view = view * rotation_matrix
+
+		# Apply eye transformation
+		var translation = new Matrix.identity(4)
+		translation.translate(diff, 0.0, 0.0)
+		view = view * translation
+
+		# Use a projection matrix with a depth
+		var projection = new Matrix.perspective(pi*field_of_view_y/2.0,
+			display.aspect_ratio, near, far)
+
+		return view * projection
+	end
+end
+
+redef class GamnitDisplay
+
+	# With stereoscopic view, the aspect ratio (in each eye) is half of the screen
+	redef fun aspect_ratio do return super / 2.0
+end
+
+redef class App
+	redef fun frame_core_draw(display) do frame_core_stereoscopic display
+
+	# Split the screen in two, and call `frame_core_depth` for each eyes
+	protected fun frame_core_stereoscopic(display: GamnitDisplay)
+	do
+		var half_width = display.width / 2
+
+		# Left eye
+		glViewport(0, 0, half_width, display.height)
+		world_camera.mvp_matrix = world_camera.mvp_matrix_left
+		frame_core_depth display
+
+		# Right eye
+		glViewport(half_width, 0, half_width, display.height)
+		world_camera.mvp_matrix = world_camera.mvp_matrix_right
+		frame_core_depth display
+
+		# We reset the viewport for selection
+		glViewport(0, 0, display.width, display.height)
+
+		# Check for errors
+		var gl_error = glGetError
+		assert gl_error == gl_NO_ERROR else print gl_error
+	end
+end
-- 
1.7.9.5