triangle rendering engine - yiwen meng...triangle rendering engine yiwen meng & su ai 2 the...

Triangle Rendering Engine

2013

EE465 FINAL PROJECT REPORT IOWA STATE UNIVERSITY

YIWEN MENG

SU AI

TRIANGLE RENDERING ENGINE YIWEN MENG & SU AI

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Introduction

The purpose of this project is design a triangle rendering engine, which is available to

rendering computation and outputs a sequence of outputs after test bench provides three con-

secutive pairs of coordinate input for a triangle. The project require the final engine has to work

appropriately, also require to optimize it to reduce the delay time, area, power consumption as

lower as we can.

Procedure

Our first design of the Verilog Code is to confine calculation of the points in the red rec-

tangular area define the three points of the inputs, so which will save a lot of time and area cir-

cuit of calculation. The graph shows below which reveals two position of triangle will possibly

place.

Figure 1. Calculation Area of triangle render engine

In order to realize this method and because the magnitude of x1 and x2 is not so clear,

so we write a code as below to do the comparison of x1 and x2 to set the smaller value to rx0,

and set the larger value to rx1.

Figure 2. Code for Comparison


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The picture below display the input, output and register in our design. We have rx0 and

rx1 just as we described above. These two stores the value of the x-axis to define the calcula-

tion area in the design. rx and ry as coordinates of the cursors, which will go through the points

of the rectangular area one by one to find the points in the triangle. The register a1 to a3, b1 to

b3, x1 to x3, y1 to y3 are registers to store the input value. The register data is x and y stores

the value from inputs. The counter is flag to indicate the input and send the value of input to

each register in our design. The finish is a flag to indicate whole calculation is finished. The im-

port is a flag to indicate if there are inputs from the test bench. The compare is a flag to indicate

whether the comparison of x1 and x2 is finished or not.

Figure 3. Input, Output and Register

The picture below revels how we send the value of the inputs to our registers. As the flag coun-

ter increase, it will send the input value to the store registers one by one. After importing all the

inputs, we set the busy signal to one to indicate the calculation of the points.

Figure 4. The Importing Method


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For the calculation, we divided rectangular calculation area to the upper sub-rectangle and

lower sub-rectangle by the value of y2, so in each sub-rectangle area, we only have one line to

do the calculation and comparison, which highly saves the registers to store the calculation

value and the area for another multipliers.

Figure 5. Two Sub-Rectangles Calculation Area.

As you can see in the code below, we divided the calculation into two sub-areas based

on the value of ry. So we defined area as ry <= y2; r2 < ry <=y3. We do the calculation of the

points when busy signal equal to 1. And for each sub-area, we only defined one register for the

line which we use to figure out whether the point is in the triangle or not. By doing so, not only

did we save the area for the register and multiplier for the calculation, but also we save the

time for calculation. We set the beginning point of the cursor at the left lower corner of the

whole rectangular region. The Y-axis of the cursor we first increase one by one, and the calcula-

tion will begin after the coordinates was changed. After the X-axis of the cursors equals to rx1

which is the larger value of X-axis of the input. We set the X-axis to rx0 which is the smaller

value of x-axis input, and we set the Y-axis of the cursor increased by one. After the cursor go-

ing from one point to another point from the left lower corner of the rectangular calculation

area to its right upper corner. We finished the calculation and send out the output which are

the coordinates of points in the triangle.


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Figure 6. Code for Calculation

After cursor reach the right upper corner of the first rectangular calculation area. The machine

will start to do the calculation of the second triangle. Also we first do the comparison of the x-

axis of the inputs to define the second rectangular calculation area. After that we sets the cur-

sor at the left lower corner and do the calculation again. The register round will increase by one

which means the machine is doing the calculation of the second triangle now. After it finished

the calculation of two triangles. The register finished will be changed to one.

Figure 7. Code for Changing from triangle 1 to 2


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Results of First Version Engine

This is the transcript after the simulation. As you can see in the red box. All the outputs

of the triangle rendering engine we designed here match all the results. And total time is

105000ns.

Figure 8. The transcript after the simulation of the first Triangle rendering engine

Figure 9. The waveform of the results from the simulation of the first version of the triangle rendering en-

gine

The two registers rx and ry are the value of the coordinates of x-axis and y-axis of the

cursor, relatively. As you can see in the red box of the waveform below, the register rx will in-

creased from 001 to 111 one by one. After it reached to 111, it will go back to 001. At the same


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time, the register ry will increased by one. As you can see yellow box below, we only have one

register to do the calculation and comparison for the cursor each time. And it will decide

whether the cursor is in the triangle or not.

Figure 10. Waveform of the register rx, ry and line

RTL compiler

Figure 11. The layout of the first version of triangle rendering engine after doing RTL compiling


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Figure 12. The report of the power and area

Figure 13. The timing report of the slack time


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The encounter synthesis

Figure 14. The floor plan in the encounter

Figure 15. The layout of the triangle rendering engine in encounter


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Figure 16. The report of timing and power in encounter

Figure 17. The measurement of the area for the layout in encounter, the size = 114.625 * 227.200


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Optimization

The basic idea of the optimization is to reduce the numbers of the calculation to the minimum,

so it can reduce the power consumption and the delay time for the design. The power con-

sumption is a major problems nowadays. Therefore, we focus on solve power consumption

problems, and do our best to reduce it as much as we can. At same time, put area and delay

time change in control.

Methodology and procedure

We notice that the starting point of the triangle is the x1 and y1, and it is in the triangle

region, so we decided to start the cursor at x1 and y1, and send it to output without cal-

culation. After that we set a cursor to the beginning point of line above that, and do the

regular calculation of the points one by one. Besides, we also find the phenomenon that

all the points whose value of y-axis equals to y2 are all in the triangle, so we also just send

these points to the output without calculation.

Figure 18. The design of the calculation area in the optimization

As you can see in the red box below, we always set the begging point of the cursor to x1 y1


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Figure 19. Code for optimization 1

The code in the red box is how we send the first point of the cursor, which equals to x1 y1 with-

out any calculation and set the cursor to the first point in the line above. As you can see in the

green box, when the y coordinates cursor equal to y2, we send out all the points on this line to

the output without any calculation.


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Figure 20. Code of optimization 2

Results of optimaztion


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The waveform in the pink box approves how we set the initial value of the register rx ry to x1

y1, and you can see the waveform in the green box, there’s a period of time in which the regis-

ter line hold at one value. That is when ry = y2, so we didn’t do the calculation for these points

on the line, but just send them to the output

Figure 21. Waveform 1

Figure 22. Waveform 2

As you can see in the red box, all the results matched well after optimization, and we also re-

duced the total delay from 105000ns to 94000ns.

Figure 23. The transcript of simulation after optimization


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Figure 24. The waveform of the results from the simulation of the first version of the triangle rendering

engine

RTL Compiler

Figure 25. The layout of the triangle rendering engine after optimization


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Figure 26. The report of area and power after optimization

Figure 27. The timing report of slack timing after optimization


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Encounter Synthesis

Figure 28.the layout of triangle rendering engine after optimization in encounter


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Figure 29. The report of power and timing in encounter after optimization 1

Figure 30. The report of power and timing in encounter after optimization 1


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Analysis

After finished all design and testing, we collected data and find out the differences be-

tween before and after optimization.

Slack time(ps) Net Power(nW) Total Area

Before Optimization 405 115739.36 1426.60

After optimization 411 82652.48 1774.8

To meet the low power consumption nowadays, we reduced net power consumption by

28.58%. However, to reach this optimization, we slightly increase the area and delayed time,

but it’s still in control. For long-term using, low power consumption will benefit more than

smaller area or lower delay time.

Summary

After all the procedures and results above, we design a triangle rendering engine and the pro-

ject meet all function requirements. The optimization process help our project works much bet-

ter and efficiently. After this project, we learned how to use Verilog to design the circuit to

solve problem. The project problem have difference with real life problems, but it’s still give us

opportunities to learn circuit development process.

Contribution

Yiwen Meng 55% Su Ai 45%

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