Bachelor-Thesis Ray-Tracing Point Clouds Christoph Wiesmeier 18. - - PowerPoint PPT Presentation

bachelor thesis ray tracing point clouds
SMART_READER_LITE
LIVE PREVIEW

Bachelor-Thesis Ray-Tracing Point Clouds Christoph Wiesmeier 18. - - PowerPoint PPT Presentation

Bachelor-Thesis Ray-Tracing Point Clouds Christoph Wiesmeier 18. November 2011 Overview 1 Challenges 2 Rendering approaches 3 Ray-Tracing Points 4 Conclusion Christoph Wiesmeier () Bachelor-Thesis Ray-Tracing Point Clouds 18. November 2011 1


slide-1
SLIDE 1

Bachelor-Thesis Ray-Tracing Point Clouds

Christoph Wiesmeier

  • 18. November 2011
slide-2
SLIDE 2

Overview

1 Challenges 2 Rendering approaches 3 Ray-Tracing Points 4 Conclusion

Christoph Wiesmeier () Bachelor-Thesis Ray-Tracing Point Clouds

  • 18. November 2011

1 / 18

slide-3
SLIDE 3

Challenges

Challenges when rendering points

Points have no surface

Rasterisation → Which shape has an infinitesimal point? Ray-Tracing → How to intersect a ray?

Points have no orientation

How to compute the shading?

Christoph Wiesmeier () Bachelor-Thesis Ray-Tracing Point Clouds

  • 18. November 2011

2 / 18

slide-4
SLIDE 4

Rendering approaches

Rendering approaches

OpenGL

First attempt

Christoph Wiesmeier () Bachelor-Thesis Ray-Tracing Point Clouds

  • 18. November 2011

3 / 18

slide-5
SLIDE 5

Rendering approaches

Rendering approaches

OpenGL

First attempt

Triangle reconstruction

Standard renderer

0Image taken from en.wikipedia.org Christoph Wiesmeier () Bachelor-Thesis Ray-Tracing Point Clouds

  • 18. November 2011

3 / 18

slide-6
SLIDE 6

Rendering approaches

Rendering approaches

OpenGL

First attempt

Triangle reconstruction

Standard renderer

Ray Tracing

Fast on huge scenes Full lighting calculation

Christoph Wiesmeier () Bachelor-Thesis Ray-Tracing Point Clouds

  • 18. November 2011

3 / 18

slide-7
SLIDE 7

Ray-Tracing Points

Recall on Ray-Tracing

Start one ray per pixel Intersect the scene Start new rays

Shadows Reflection Refraction

Combine results

Light Source Scene Object Shadow Ray View Ray Image Camera

0Image taken from en.wikipedia.org Christoph Wiesmeier () Bachelor-Thesis Ray-Tracing Point Clouds

  • 18. November 2011

4 / 18

slide-8
SLIDE 8

Ray-Tracing Points

OpenGI Ray-Tracer

Scene handling with OpenSG Support for Triangles Light computation based on normals Bounding-Volume Hierarchy GPU accelerated

Christoph Wiesmeier () Bachelor-Thesis Ray-Tracing Point Clouds

  • 18. November 2011

5 / 18

slide-9
SLIDE 9

Ray-Tracing Points

Ray-Point intersection (Spheres)

Simple No normals required Point Size?

Christoph Wiesmeier () Bachelor-Thesis Ray-Tracing Point Clouds

  • 18. November 2011

6 / 18

slide-10
SLIDE 10

Ray-Tracing Points

Ray-Point intersection (Spheres)

Simple No normals required Point Size? Problems:

Rippled surface Object grow

Christoph Wiesmeier () Bachelor-Thesis Ray-Tracing Point Clouds

  • 18. November 2011

6 / 18

slide-11
SLIDE 11

Ray-Tracing Points

Ray Point intersection (Disc)

Accurate position Flat surface Disc orientation ? Disc size ? Problem self shadowing

Christoph Wiesmeier () Bachelor-Thesis Ray-Tracing Point Clouds

  • 18. November 2011

7 / 18

slide-12
SLIDE 12

Ray-Tracing Points

Ray Point intersection (Disc)

Accurate position Flat surface Disc orientation ? Disc size ? Problem self shadowing

Christoph Wiesmeier () Bachelor-Thesis Ray-Tracing Point Clouds

  • 18. November 2011

7 / 18

slide-13
SLIDE 13

Ray-Tracing Points

Ray Point intersection (Disc)

Accurate position Flat surface Disc orientation ? Disc size ? Problem self shadowing

Christoph Wiesmeier () Bachelor-Thesis Ray-Tracing Point Clouds

  • 18. November 2011

7 / 18

slide-14
SLIDE 14

Ray-Tracing Points

Splats (Shading)

Use multiple intersection 16 nearest points Using disc intersection Local surface representation Using the nearest disc as intersection point

Christoph Wiesmeier () Bachelor-Thesis Ray-Tracing Point Clouds

  • 18. November 2011

8 / 18

slide-15
SLIDE 15

Ray-Tracing Points

Splats

Normal selected as weighted average n = N

i ni ∗ (1 − di ri )

Creates smooth surface Requires aligned normals

Christoph Wiesmeier () Bachelor-Thesis Ray-Tracing Point Clouds

  • 18. November 2011

9 / 18

slide-16
SLIDE 16

Ray-Tracing Points

Splats (aligned)

Alignment towards the ray origin Flip normal if n • ray.d ≥ 0 Weighted average as before

Christoph Wiesmeier () Bachelor-Thesis Ray-Tracing Point Clouds

  • 18. November 2011

10 / 18

slide-17
SLIDE 17

Ray-Tracing Points

Splats (aligned)

Alignment towards the ray origin Flip normal if n • ray.d ≥ 0 Weighted average as before Artifacts on edges

Christoph Wiesmeier () Bachelor-Thesis Ray-Tracing Point Clouds

  • 18. November 2011

10 / 18

slide-18
SLIDE 18

Ray-Tracing Points

Splats (runtime normal)

Calculate the normal using intersected points Normal is required for intersection test Requires more points than weighted average Increased render times

Christoph Wiesmeier () Bachelor-Thesis Ray-Tracing Point Clouds

  • 18. November 2011

11 / 18

slide-19
SLIDE 19

Ray-Tracing Points

Rendering Results

1.5M points, splats aligned

Christoph Wiesmeier () Bachelor-Thesis Ray-Tracing Point Clouds

  • 18. November 2011

12 / 18

slide-20
SLIDE 20

Ray-Tracing Points

Rendering Results

407k points, splats aligned

Christoph Wiesmeier () Bachelor-Thesis Ray-Tracing Point Clouds

  • 18. November 2011

13 / 18

slide-21
SLIDE 21

Ray-Tracing Points

Rendering Results

1M points, splats aligned

Christoph Wiesmeier () Bachelor-Thesis Ray-Tracing Point Clouds

  • 18. November 2011

14 / 18

slide-22
SLIDE 22

Ray-Tracing Points

Rendering Results

265k points, splats aligned

Christoph Wiesmeier () Bachelor-Thesis Ray-Tracing Point Clouds

  • 18. November 2011

15 / 18

slide-23
SLIDE 23

Ray-Tracing Points

Performance

Dataset Bunny Armadillo Pisa NrPoints 36k 173k 1M trace render trace render trace render ms ms ms ms ms ms Sphere 9.6 46.9 5.9 19.7 16.5 48.7 Disk 7.4 38 9.2 25.3 26.3 119 Multi mean 9.2 38 12.4 28 38.9 135 Multi aligned 9.3 38.5 12.3 28 39 135 Multi runtime 39 102 15 32 85 183

Christoph Wiesmeier () Bachelor-Thesis Ray-Tracing Point Clouds

  • 18. November 2011

16 / 18

slide-24
SLIDE 24

Conclusion

Conclusion / Further work

Good rendering results Interactive rendering Limited number of Points Does not work on noisy datasets Requires equal distributed points Problems on sharp edges Runtime normal estimation requires normals

Christoph Wiesmeier () Bachelor-Thesis Ray-Tracing Point Clouds

  • 18. November 2011

17 / 18

slide-25
SLIDE 25

Conclusion

End of Presentation

Questions?

Christoph Wiesmeier () Bachelor-Thesis Ray-Tracing Point Clouds

  • 18. November 2011

18 / 18