Draw calls run a program's shaders on staged GPU data.
Note that in WebGL2 it is possible to disable the rasterization stage, preventing draw calls from actually drawing anything. This mainly is used in combination with transform feedback.
You can use
model.clear() to clear the default framebuffer, or
framebuffer.clear() to clear a specific framebuffer, or just call
Framebuffers are container objects that hold one or more textures and/or renderbuffers, representing color buffers, depth buffers, stencil buffers etc.
Framebuffers hold one or more textures and/or renderbuffers. Renderbuffers are optimized for rendering performance, whereas textures (when used as render targets) support readback of rendered pixels.
Rendering is affected by WebGL parameters, such as blending, depth testing, culling, etc.
A viewport specifies how clip space will be mapped to pixels on the WebGL canvas.
A scissor rect limits rendering on the current viewport.