Based on stb_to_utf8() from github.com/nothings/stb/

Not optimal but we very rarely use this function.

Initializes the mesh as a plane

Returns the result of performing a irradiance integral over the portion of the hemisphere covered by a region with angular radius = theta

Project sample onto SGs

Computes a radical inverse with base 2 using crazy bit-twiddling from "Hacker's Delight"

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Returns the contents of a file as a string

We don't use g.FontSize because the window may be != g.CurrentWidow.

Renders all meshes in the model, with shadows

Render shadows for all spot lights

Renders meshes using cascaded shadow mapping

Internal ImGui functions to render text RenderText***() functions calls ImDrawList::AddText() calls ImBitmapFont::RenderText()

Returns a 2D sample from a particular pattern using correlated multi-jittered sampling [Kensler 2013]

Returns a random direction from within a cone with angle == theta

Returns the PDF of of a single uniform sample within a cone