Billboard example

examples/Effects/Billboards/main.lua

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+-- red puffs are billboards oriented in GLSL
+-- blue puffs are billboards oriented in Lua
+
+function lovr.load()
+  -- puff texture
+  puffImageSize = 128                                                         -- try 16
+  puffImage = lovr.data.newImage(puffImageSize, puffImageSize)
+  for x = 0, puffImageSize - 1 do
+    for y = 0, puffImageSize - 1 do
+      local radius = puffImageSize / 2 - 1
+      local distanceFromCenter = vec2(radius, radius):distance(vec2(x, y))
+      local depth = math.sqrt(radius^2 - distanceFromCenter^2)
+      puffImage:setPixel(x, y, 1, 1, 1, depth / radius)
+      lovr.math.drain()
+    end
+  end
+  puffTexture = lovr.graphics.newTexture(puffImage)
+  -- puffTexture:setFilter('nearest')                                         -- try uncommenting
+  puffMaterial = lovr.graphics.newMaterial(puffTexture)
+
+  -- puff positions
+  redPuffs = {}
+  for i = 1, 100 do
+    table.insert(redPuffs, {
+      position = lovr.math.newVec3(
+        lovr.math.random() - .5, 
+        lovr.math.random() - .5 + 1.7,
+        lovr.math.random() - .5
+      )
+    })
+  end
+  bluePuffs = {}
+  for i = 1, 100 do
+    table.insert(bluePuffs, {
+      position = lovr.math.newVec3(
+        lovr.math.random() - .5, 
+        lovr.math.random() - .5 + 1.7,
+        lovr.math.random() - .5
+      )
+    })
+  end
+
+  -- red puff billboard shader
+  redPuffVertex = [[
+    uniform vec3 headPosition;
+
+    mat4 target(vec3 from, vec3 to, vec3 up) {
+      mat4 m;
+      vec3 z = normalize(from - to);
+      vec3 x = normalize(cross(up, z));
+      vec3 y = cross(z, x);
+      m[0] = vec4(x, 0);
+      m[1] = vec4(y, 0);
+      m[2] = vec4(z, 0);
+      m[3] = vec4(from, 1);
+      return m;
+    }
+
+    vec4 position(mat4 projection, mat4 transform, vec4 vertex) {
+      vec3 puffPosition = lovrModel[3].xyz;
+      vec3 puffScale = vec3(length(lovrModel[0]), length(lovrModel[1]), length(lovrModel[2]));
+      mat4 billboardModel = target(puffPosition, headPosition, vec3(0, 1, 0));
+      billboardModel *= mat4(
+        puffScale.x, 0,           0,           0,
+        0,           puffScale.y, 0,           0,
+        0,           0,           puffScale.z, 0,
+        0,           0,           0,           1
+      );
+      return projection * lovrView * billboardModel * vertex;
+    }
+  ]]
+  defaultFragment = [[
+    vec4 color(vec4 graphicsColor, sampler2D image, vec2 uv) {
+      return graphicsColor * lovrDiffuseColor * lovrVertexColor * texture(image, uv);
+    }
+  ]]
+  redPuffShader = lovr.graphics.newShader(redPuffVertex, defaultFragment)
+
+  lovr.graphics.setBackgroundColor(0, .5, 1)
+end
+
+function lovr.draw()
+  -- red puffs
+  lovr.graphics.setColor(1, .9, .9)
+  lovr.graphics.setDepthTest('lequal', false)
+  lovr.graphics.setShader(redPuffShader)
+  redPuffShader:send('headPosition', {lovr.headset.getPosition('head')})
+  for _, puff in pairs(redPuffs) do
+    lovr.graphics.plane(puffMaterial, puff.position, .1)
+  end
+  lovr.graphics.setDepthTest('lequal', true)
+  lovr.graphics.setShader()
+
+  -- blue puffs
+  lovr.graphics.setColor(.9, 1, 1)
+  lovr.graphics.setDepthTest('lequal', false)
+  for _, puff in pairs(bluePuffs) do
+    puff.orientation = quat(mat4():target(puff.position, vec3(lovr.headset.getPosition('head'))))
+    lovr.graphics.plane(puffMaterial, puff.position, .1, .1, puff.orientation)
+  end
+  lovr.graphics.setDepthTest('lequal', true)
+end