Polygon count, file size, and rendering times can constrain 3D graphics. A high polygon count means more complex models but larger file sizes that require more processing power. If the polygon count or file size is too high for the available memory and processing, it can cause issues rendering animations or walkthroughs in real-time. While polygons make up 3D objects, triangles are how they are rendered by graphics hardware. Polygon count refers to the number of triangles, and a high triangle or vertex count can impact performance. Rendering is the process of generating 2D images from 3D scene data and requires solving lighting and other effects, which may exceed real-time capabilities without rendering to temporary files.

1. Constraints
Polygon Count
There are lots of advantages to making 3d graphics compared to 2d graphics, however there are
limitations to making 3d graphics which might not occur in 2d. For example, when creating 3d
graphics you have to consider your poly count? Your poly count is the amount of poly’s being
rendered per frame, you render your 3d graphics in a wire frame state first rather than shaded
because it is much quicker. The polys are what make up the 3d object and the more complex and
detailed the object the higher the poly count will be.
File size
Another problem with having a high poly count is that the file size will be very high, an this general
means you will need a high quality CPU (Central processing unit) to render your work. The better
the CPU the more poly’s it can handle and render at once so this gives you quicker work pace but
this type of high end equipment has a high end price tag and is expensive so not everyone can
afford this type of equipment.
http://bigcostas.wordpress.com/limitations-of-3d-poly-count-file-size-and-rendering-times/
How would polygon count and file size cause constraints in rendering a walkthrough?
(3D animation)
If the polygon count is too high and you have a lack of memory this is one issue for that reason as i
said before in you’re have a limited amount of memory then you won't need to add more into your
motherboard as your scenes get bigger the more memory it will use. all these you add more animate
all takes up memory. 3d programs are very memory intensive. If your computer cannot handle the
count then i would stick to modelling small scenes until you have the memory.
http://uk.answers.yahoo.com/question/index?qid=20130516122638AAJH9g5
Polygons vs Triangles
The two common measurements of a game character's 'cost' are polygon count and vertex count.
Polygon is interchangeable with triangle in these measurements, as GPUs only see vertices and
triangles, not 4+ sided polygons. Depending on the use, a game character may stretch anywhere
from 200-300 triangles, to 40,000+ triangles. A high-end third-person console or PC game may use
many vertices or triangles per character, and an iOS tower defence game might use very few per
character.
When a game artist talks about the poly count of a model, they really mean the triangle count.
Games almost always use triangles not polygons because most modern graphic hardware is built to
accelerate the rendering of triangles. The polygon count that's reported in a modelling app is always
misleading, because a model's triangle count is higher. It's usually best therefore to switch the
polygon counter to a triangle counter in your modelling app, so you're using the same counting
method everyone else is using.Polygons however do have a useful purpose in game development. A
model made of mostly four-sided polygons (quads) will work well with edge-loop selection &

2. transform methods that speed up modelling, make it easier to judge the "flow" of a model, and
make it easier to weight a skinned model to its bones. Artists usually preserve these polygons in
their models as long as possible. A quad polygon shape can be triangulated two different ways.
When a model is exported to a game engine, the polygons are all converted into triangles
automatically. However different tools will create different triangle layouts within those polygons. A
quad can end up either as a "ridge" or as a "valley" depending on how it's triangulated. Artists need
to carefully examine a new model in the game engine to see if the triangle edges are turned the way
they wish. If not, specific polygons can then be triangulated manually.
When using a NormalMap some tools may require an artist to convert the model into all triangles
before baking. If the triangles are flipped differently when the model is exported than they were
when the normal map was baked, this can cause the final normal-mapped lighting to zig-zag across
the model. Triangulating before baking will solve this.
Triangle Count vs. Vertex Count
Vertex count is ultimately more important for performance and memory than the triangle count, but
for historical reasons artists more commonly use triangle count as a performance measurement. On
the most basic level, the triangle count and the vertex count can be similar if the all the triangles are
connected to one another. 1 triangle uses 3 vertices, 2 triangles use 4 vertices, 3 triangles use 5
vertices, 4 triangles use 6 vertices and so on.
However, seams in UVs, changes to shading/smoothing groups, and material changes from triangle
to triangle... are all treated as a physical break in the model's surface, when the model is rendered
by the game. The vertices must be duplicated at these breaks, so the model can be sent in render
able chunks to the graphics card.
Overuse of smoothing groups, over-split age of UVs, too many material assignments (and too much
misalignment of these three properties), all of these lead to a much larger vertex count. This can
stress the transform stages for the model, slowing performance. It can also increase the memory
cost for the mesh because there are more vertices to send and store.
http://wiki.polycount.com/PolygonCount
Rendering
Rendering is the process of generating an image from a model (or models in what collectively could
be called a scene file), by means of computer programs. Also, the results of such a model can be
called a rendering. A scene file contains objects in a strictly defined language or data structure; it
would contain geometry, viewpoint, texture, lighting, and shading information as a description of
the virtual scene. The data contained in the scene file is then passed to a rendering program to be
processed and output to a digital image or raster graphics image file. The term "rendering" may be
by analogy with an "artist's rendering" of a scene. Though the technical details of rendering methods
vary, the general challenges to overcome in producing a 2D image from a 3D representation stored
in a scene file are outlined as the graphics pipeline along a rendering device, such as a GPU. A GPU is

3. a purpose-built device able to assist a CPU in performing complex rendering calculations. If a scene is
to look relatively realistic and predictable under virtual lighting, the rendering software should solve
the rendering equation. The rendering equation doesn't account for all lighting phenomena, but is a
general lighting model for computer-generated imagery. 'Rendering' is also used to describe the
process of calculating effects in a video editing program to produce final video output.
http://en.wikipedia.org/wiki/Rendering_(computer_graphics)
Lighting
In order to make the model to have a more realistic appearance, one or more light sources are
usually equipped during the scene of transforming the model. However, this stage cannot be
reached without completing the 3D scene being transformed into the view space; the view space is
where the camera is placed at the origin and aimed in a way that the camera is looking in the
direction of the negative z-axis, with the y-axis pointing upwards and the x-axis pointing to the right.
http://en.wikipedia.org/wiki/Real_Time_rendering
What is rendering?
Any time Final Cut Pro must perform more calculations than your computer can handle in real time,
you need to render. Rendering is the process of creating temporary video and audio render files for
segments of your sequence that Final Cut Pro cannot play in real time. When you render a segment
of your sequence, Final Cut Pro substitutes a render file for the segment during playback. Render
status bars above the ruler in the Timeline indicate which sections can play back in real time and
which segments require rendering. Because rendering takes time away from the editing process, the
goal is to render as little as possible. For more information about real-time playback, see Using RT
Extreme. Rendering is generally required for: •The use of filters, transitions, generators, or any
combination of effects that exceeds your computer’s real-time playback capabilities. High-quality
final output. Real-time effects that play back at preview quality must ultimately be rendered for
high-quality video output. Video clips using codecs that Final Cut Pro can’t play in real time. Multiple
audio tracks that exceed your real-time playback limit. Clips with audio effects that require too much
processing power. Some nested sequences, which can include layered Photoshop files.
http://documentation.apple.com/en/finalcutpro/usermanual/index.html#chapter=85%26section=1
%26tasks=true