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/*
* 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;
}
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