message: better renderer depthMask handling
diff: @@ -211,8 +211,10 @@ namespace Renderer {
  state.enable(gl.BLEND)
  for (let i = 0, il = renderables.length; i < il; ++i) {
  const r = renderables[i]
  - state.depthMask(r.values.uAlpha.ref.value === 1.0)
  - if (!r.state.opaque) renderObject(r, variant)
  + if (!r.state.opaque) {
  + state.depthMask(false)
  + renderObject(r, variant)
  + }
  }
  } else { // picking & depth
  for (let i = 0, il = renderables.length; i < il; ++i) {
  