Java-only version of SkAR: drawing on android Canvas

Bug: skia:
Change-Id: I3b85fac93a2854d1575f71554e2a7da66e8a6a6f
Reviewed-on: https://skia-review.googlesource.com/138920
Reviewed-by: Mike Reed <reed@google.com>

1 files changed, 40 insertions, 0 deletions

diff --git a/platform_tools/android/apps/skar_java/src/main/assets/shaders/plane.vert b/platform_tools/android/apps/skar_java/src/main/assets/shaders/plane.vert
new file mode 100644
index 0000000000..9ac5a6db27
--- /dev/null
+++ b/platform_tools/android/apps/skar_java/src/main/assets/shaders/plane.vert
@@ -0,0 +1,40 @@
+/*
+ * Copyright 2017 Google Inc. All Rights Reserved.
+ * 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.
+ */
+
+uniform mat4 u_Model;
+uniform mat4 u_ModelViewProjection;
+uniform mat2 u_PlaneUvMatrix;
+uniform vec3 u_Normal;
+
+attribute vec3 a_XZPositionAlpha; // (x, z, alpha)
+
+varying vec3 v_TexCoordAlpha;
+
+void main() {
+   vec4 local_pos = vec4(a_XZPositionAlpha.x, 0.0, a_XZPositionAlpha.y, 1.0);
+   vec4 world_pos = u_Model * local_pos;
+
+   // Construct two vectors that are orthogonal to the normal.
+   // This arbitrary choice is not co-linear with either horizontal
+   // or vertical plane normals.
+   const vec3 arbitrary = vec3(1.0, 1.0, 0.0);
+   vec3 vec_u = normalize(cross(u_Normal, arbitrary));
+   vec3 vec_v = normalize(cross(u_Normal, vec_u));
+
+   // Project vertices in world frame onto vec_u and vec_v.
+   vec2 uv = vec2(dot(world_pos.xyz, vec_u), dot(world_pos.xyz, vec_v));
+   v_TexCoordAlpha = vec3(u_PlaneUvMatrix * uv, a_XZPositionAlpha.z);
+   gl_Position = u_ModelViewProjection * local_pos;
+}