Variable points size (with distance) on Processing 2.0

Core Library Questions

jcobreros

Variable points size (with distance) on Processing 2.0

in Core Library Questions • 1 year ago

Hi. I recently tried Processing 2.0 and I've noticed something I love. If I draw 3d points (OPENGL or P3D), their apparent size changes with perspective (Instead of being a fixed number of pixels). They are also round.

(Example: http://imgur.com/W7FaI)

Does this come from OpenGl 2.0? or is it particular to the processing implementation?

I'm in the process of learning pure openGl and points don't behave like this normally. If it's a processing implementation (like substituting points for circles or something like that), it is pretty fast. If it's an openGl feature, does anyone know how it's used?

This takes point clouds to a new level for me (Without having to get into textures).

Thanks!!

Replies(3)

andres

Re: Variable points size (with distance) on Processing 2.0

1 year ago

The point (and line) rendering is entirely implemented in Processing through shaders, this allows for greater flexibility and things like round points and perspective correction. For lines, in fact, you can disable perspective correction in the case you don't want stroke lines to became smaller when moving away from the camera:

hint(DISABLE_PERSPECTIVE_CORRECTED_LINES)

jcobreros

Re: Variable points size (with distance) on Processing 2.0

1 year ago

Hey Andres, thanks for the reply.

I've been investigating and found a parameter that you can modify to achieve similar effects in OpenGL (I know this is not an OpenGL forum but i hope someone finds this useful).

GLPointParameter(PointParameterName.PointDistanceAttenuation, vector3);
vector3 = { fixed, linear, quadratic }

For fixed, linear, and quadratic decay with distance.

andres

Re: Variable points size (with distance) on Processing 2.0

1 year ago

Cool, thanks for pointing out to the distance attenuation for points. Although the current point rendering algorithm in 2.0a7 is more flexible and allows for rounded points and has no size limit, it is also more expensive (each point is actually a triangle fan). I'm planning to use hardware points rendering, together with the attenuation function you mentioned, if the strokeCap is set to RECT and the point size is below the hardware-supported limit. This will result in faster rendering of points when they are small enough and not rounded points are needed.

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