Recent examples cleanup

[bhouston]

I cleaned up the recent tonemapping, transparency and envmap_hdr examples to look better and have better defaults, and more meaningful options. I also fixed one bug introduced by some of my recent PRs being slightly incompatible with each other.

The examples now look like this now:

[bhouston]

Links to the live examples:

http://ci.threejs.org/api/pullrequests/8256/examples/webgl_tonemapping.html
http://ci.threejs.org/api/pullrequests/8256/examples/webgl_materials_envmaps_hdr.html
http://ci.threejs.org/api/pullrequests/8256/examples/webgl_materials_transparency.html

[mrdoob]

Thanks! I would revert to black background though.

[mattdesl]

Hmm why is this param now using UnsignedByteType? Doesn't that mean the PMREMGenerator is getting clamped colours?

[bhouston]

If you use half or float, it unpacks the *.hdr maps into float or half buffers as appropriate. If you specify UnsignedByte, it keeps the original RGBE byte encoding and does live decoding within the fragment shader (because texture.encoding = THREE.RGBEEncoding.) RGBE is 8bit per channel, but the E is the exponent. Thus it is 16 bit floating point with a shared 8 exponent in the former:

r = R * 2^ ( E * 255 - 128.0 )
g = G * 2^ ( E * 255 - 128.0 )
b = B * 2^ ( E * 255 - 128.0 )

[mattdesl]

Ok, good to know.

Switching it to FloatType produces errors on Windows (ANGLE maybe?). FloatType works fine on OSX.

Error: WebGL: generateMipmap: Texture at base level is not unsized internal format or is not color-renderable or texture-filterable.

[bhouston]

FloatType worked for me on my Windows PC.

I believe it is related to asking for the right extension before using it. You need both OES_texture_float and oes_texture_float_linear available for float, and oes_texture_half_float and oes_texture_half_float_linear for Half support.