代写COMP3811程序、代写Python，Java编程

日期：2021-10-27 10:57

COMP3811: Computer Graphics

Coursework 1

Rasterization

Due Date: 5 November 2021, 5 pm

Marc de Kamps, Markus Billeter

October 22, 2021

Marking

This coursework is summative and counts towards your final mark for 30 % (total coursework counts

for 100 %).

Submission Instruction and Note on Plagiarism

Submission should be done through the VLE by the due date. Submissions through the SSO will be

ignored and result in 0 marks. Your submission should be in a single tar (not rar!) file that contains

a report and source code. Source code must be provided with a Makefile and must compile and run

on the School’s machines (e.g., feng-linux, Bragg building machines).

Source code that does not compile and run will not be looked at and no marks will be awarded

to any programming exercise that it relates to. The report is basis for assessment, with the source

code as supporting evidence for assertions made in the report. Answer all the questions and provide

the explanations that are asked for. Refer to your code in explanations, but do not provide answers

like: ’see source code’.

You are allowed to discuss ideas with colleagues. You must program independently and not base

your submission on any other code than is provided with this coursework assignment, which is in

a tar file called cw1.tar.gz, which is located in the coursework 1 folder on the VLE, the same

folder which contains this specification. Changing variable names in someone else’s code is not a

good idea.

Drawing lines

Unpack the tar file. Run qmake and make as you have been taught in the tutorial. Run the resulting

pixelate application. The application window shows a rasterized screen with a single red pixel.

The PixelWidget.cpp contains a method DefinePixelValues

v oi d Pi x elWi d g et : : D e f i n e P i x e l V a l u e s ( ) {

S e t P i x e l ( 1 9 , 9 , RGBVal ( 2 5 5 , 0 , 0 ) ) ;

}

It is clear that by adding SetPixel calls it is possible to construct larger primitives, made up from

pixels. We use this widget to make the effects of rasterization more visible.

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Assigment 1: First make sure that you are able to set arbitrary pixels (within the widget) to arbitrary

RGB values. Adopt the following convention: a pair of floats define a pixel on the screen. The first

gives the horizontal distance in number of pixels from the top left corner, the second the vertical

distance. Add a method call DrawLine to the PixelWidget class that is able to take four floating

point values, the first two defining the starting point, and the second two the end point, and that

draws a line of white pixels between them. Use the parameterised version of a line to calculate the

pixels that will be hit between the two points. You must ensure that every pixel that contains the

mathematical ideal of the line lights up. This entails choosing steps that are small enough to ensure

you hit every pixels, but large enough to be not overly wasteful. Motivate your choice for a step

size. Make sure that this method is called in paintEvent, so that a line is drawn. Add a screenshot

to the report and explain whether the result is as expected.

[3 marks]

Assignment 2: Adapt the method you have just created so that it is able to accept an RGB value (use

struct RGBVal) for starting point, another one for end point and interpolate the colour along the line.

Again, add a screenshot to your report explaining the results.

[4 marks]

Assignment 3: Create a method that accepts three points and associated RGB values. Use barycentric

coordinates to interpolate pixels that are part of the triangle.

[4 marks]

Assignment 4: Implement the half plane test for determining whether a point is inside or outside

the triangle. Create a function called IsInside that takes as arguments the three vertices (each one

specified by two floats), defining the triangle and a point in pixel coordinates. Apply this function

to all pixels in your image. Produce a file which lists the barycentric coordinates of each pixel and

the result of your function. Perform a comparison between the results of your function and the

barycentric coordinates (you can do this in a separate script if you like). In your report describe the

method, and comment on whether the results are as expected.

[3 marks]

Assignment 5: Create a ppm image from an interpolated triangle. The format for such images are

defined here: http://paulbourke.net/dataformats/ppm/.

[1 marks]

[15 marks total]

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