1 / 17

170 likes | 367 Vues

3D graphics. For client processors it ’ s the big gorilla of compute requirements. Image creation/ reconstruction/ 2 and 3D projection/ animation/ visualization Must be interactive for image creation and smoothly(visually) manage motion and update dynamics. 3D graphics.

Télécharger la présentation
## 3D graphics

**An Image/Link below is provided (as is) to download presentation**
Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.
Content is provided to you AS IS for your information and personal use only.
Download presentation by click this link.
While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

**3D graphics**• For client processors it’s the big gorilla of compute requirements. • Image creation/ reconstruction/ 2 and 3D projection/ animation/ visualization • Must be interactive for image creation and smoothly(visually) manage motion and update dynamics**3D graphics**Some basic requirements: • smooth motion 15 frames/sec • frame size 1260 x 1024 down to 512 x 512 • pixel 24b (3 colors, RGB) + 8b color control sometimes double buffered and z buffered (3D) up to 96b total. • frame size x pixel size = frame buffer • frame buffer also used to refresh video @ 30 or 60 Hz**Operations, simple 2D type**• Limited primitives: polygon, line, circle, ellipse • ops: scale, translate, overlay and clip • typical op is S op D =D; op is replace, or, xor, and … applied to blocks of pixels • computations linear, y = mx + b, or quadratic x2 + y2 = R2 ; mostly on index values…needs say 16b, sometimes 32b FP computation**Clipping**• Requires finding point at which line (edge) intersects plane or another line then filling included spaces…need to find intersect line • Computation of the form t = NxDP/ D**Video controllers and VRAM**• Video controller is responsible for CRT refresh usually 30 or 60 Hz. • Must access the frame buffer for data, can be a significant memory bandwidth limit… the larger the DRAM the worse the problem • Solution is VRAM; two ported DRAM, one is a serial port which reads out all pixels in a scan line in one cycle then buffers and forwards it.**2D transformations**• Translate (move), Scale (change size) and Rotate…can be viewed as a matrix, M operating on a point, P(x,y) • M is a 3 x 3 matrix expressing T, S and R parameters… Reducible to 4 mpy and 4 adds per point.**3D transformations**• Need now to transform object to a new coordinate system…then do scaling, rotation…then retransform to viewer’s plane • M now a 4 x 4 matrix applied several times • Maybe 25 multiplies and 18 adds per point • Note: not all points need transformation, only vertices**Triangles and polygons**• Gather pixels into objects with shared edges then deal only with transforming the vertices and the normal surface vector. • Maybe 100 pixels per triangle or polygon; fine resolution might use 10 pixels/ object • Object may consist of 10,000 triangles, 30k vertices … not 1M pixels**Shading/ lighting**• Diffuse ambient light creates no shading... Simplest • Illumination can vary by angle between N (normal to the polygon) and L (the source) • Source of illumination can be a point or a region (expressed as cosng). The larger the n the narrower the beam • Compute N and L across polygon face**Shading**• Can interpolate shade across a polygon • Gourand shading interpolates shade across edges, reduces effect of intensity change. • Phong shading (and illumination) interpolates surface normal vector across polygons then interpolates illumination.**Texture**• Surface of object polygons perturbed by applying “bump map”; add map values to polygon values.**Shadows and beyond**• Can be computationally intensive, project each polygon on light source find projection on other polygons • 3D shadows, transparency, fog and atmospherics all complicate the computation.**Compute requirements**Assume a very simple image. • 10k triangles with 100 pixels/ triangles • 1024x1024 RGB display updated 10 frames/sec • diffuse ambient illumination • shading, no shadows • no texture, fog, transparency • no clipping from multiple objects**Compute requirements**• Transform/ rotate takes 25 multiplies & 18 adds/vertex … 10k x 3 = 30k vertices • Computing viewer’s projection of the object surface (which triangles are in view) takes 18 multiplies & 14 adds / vertex • Simple lighting 12 mpy & 5 adds/vertex • Clipping 3 divides/ vertix • Plus…**Compute requirements**• Net about 2M multiplies &1.4M adds/frame • About 30 Mflops depending on image clipping adds 1M divides/sec • Plus about 50 Maps to the frame buffer. • Refined images (10 pixels/polygon) plus Phong illumination and Gourand shading plus shadows, texture, etc. …100x to 400x • WHEW**Designing for multimedia**Must support very high bandwidth arithmetic • pipelined integer and fp • optimized for 8, 16 and 32b operands • instructions set support for sub word concurrency • divide and sqrt can be important as well as trig functions.**Designing for multimedia**Must support very high bandwidth memory • structured memory access VRAM • VRAM on chip? • structured L1 D cache • large L2; maybe also structured or bypassed as with vector processor.

More Related