VT redraw on request

Former-commit-id: 3ada71215d9291760704a982cc3952061dbc7afe
Former-commit-id: ca1495e668e88bc7214429472ad918621a650189

assets/.gitattributes

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+*.{psd,tga,ogg} filter=lfs diff=lfs merge=lfs -text

assets/test.frag

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+#ifdef GL_ES
+    precision mediump float;
+#endif
+
+varying vec4 v_color;
+varying vec2 v_texCoords;
+uniform sampler2D u_texture;
+uniform mat4 u_projTrans;
+
+void main() {
+        vec3 color = texture2D(u_texture, v_texCoords).rgb;
+        float gray = (3.0 * color.r + 4.0 * color.g + color.b) / 8.0;
+        vec3 grayscale = vec3(gray);
+
+        gl_FragColor = vec4(grayscale, 1.0);
+}

assets/test.vert

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+attribute vec4 a_position;
+attribute vec4 a_color;
+attribute vec2 a_texCoord0;
+
+uniform mat4 u_projTrans;
+
+varying vec4 v_color;
+varying vec2 v_texCoords;
+
+void main() {
+    v_color = a_color;
+    v_texCoords = a_texCoord0;
+    gl_Position = u_projTrans * a_position;
+}