Apple Maps

Cesium

OpenGL Pipeline

It is the tool you use to take data and turn it into pixels. 

You have to do everything yourself...

GLSL

GL Shading Language

http://webglfundamentals.org/

Vertex Shader

Fragment Shader

Clipspace

Coordinates

Color

Vertex Shader + Fragment Shader = Program

1 app can = many programs

Buffer

A way of getting vertex and other per vertex data on the GPU.

gl.createBuffer - creates a buffer

gl.bindBuffer - sets that buffer as the buffer to be worked on

gl.bufferData - copies data into the buffer

Vertex Shader

Transforms each vertex's position in the model (vector tile coordinates) to the 2D coordinate at which it appears on the screen.

Setting a variable gl_position that gets the clipspace values for the current vertex.

Vertex Shader Data Sources:

Attributes - data pulled from buffers

Uniforms - values that are constant for all                          vertices in a draw

Textures - data from pixels / texels.

The vertex shader is called 1 x per vertex.

Fragment Shader

Provides a color for the current pixel being rasterized.

Sets the global variable gl_FragColor.

Fragment Shader Data Sources:

Varyings - data passed from the vertex                           shader and interpolated.

Uniforms - values that stay the same for                          every pixel of a single draw call

Textures - data from pixels / texels

The fragment shader is called 1 x per pixel.

The process of rendering a map generally means taking raw geospatial data and making a visual map from it.

Mapnik

The most widely used open source map renderer.

The vector data is rendered to pixels on the fly, on your local machine with OpenGL.

Esri's Fork of mapbox-gl-js

style.json

Rather than styling the map with CartoCSS or SLD, we have a style.json document that determines how the data is drawn on the map.

MapboxGL Style Reference

If you modify a value in the style sheet, all you have to do is call map.render()

The amount of work that this "low level map renderer" is requiring to get to a production level library is extensive...

But, it will completely change how maps look and behave for the rest of the industry outside of Google and Apple.

Line Anti-Aliasing

GL does draw lines, but it only knows to turn on pixels in between vertices...

https://www.mapbox.com/blog/drawing-antialiased-lines/

Fonts

You have to make your own "glyph atlas" and used signed distance weighting from the glyphs to set your font size...

https://www.mapbox.com/blog/text-signed-distance-fields/

Tracking

and kerning...

Ad hoc Projection?

Oregon State University

Adaptive Composite Projection

Cool NASA Demo