Overview
+Give a high-level overview of what you implemented in this project. Think about what you've built as a whole. Share your thoughts on what interesting things you've learned from completing the project.
++ In this project, we implemented a spring-mass-damper system to represent the physical simulation of cloth and its interactions with other objects. + We observed the differences between spring and damping constants applied to the system and how it changed the behavior of the cloth independently + as well as its behavior in its collisions with other objects. Finally, we implemented shaders on a cloth as it draped over a sphere using OpenGL + and the Blinn-Phong shading model. We also implemented texture, bump, displacement, and mirror maps as shaders. +
+Part I: Masses and springs
++ Take some screenshots of scene/pinned2.json from a viewing angle where you can clearly see the cloth wireframe to show the structure of your point masses and springs. + Show us what the wireframe looks like (1) without any shearing constraints, (2) with only shearing constraints, and (3) with all constraints. +
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Part 2: Simulation via numerical integration
++ Describe the effects of changing the spring constant ks; how does the cloth behave from start to rest with a very low ks? A high ks? +
++ With a very low ks, the springs are held together much more loosely. There is less of a force in between the springs, so they are not held + together as tightly. The effect is opposite for a high ks, where the cloth is much more rigid. It does not fall as much in the middle: +
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+ What about for density? +
++ With a very low density, the cloth is not weighed down as much. It has a much smoother appearance when it falls. In contrast, with a high + density, the middle of the cloth sinks much more, as the fabric is heavier and the middle cannot be supported as much by the pinned + points that a lower density cloth would be. This difference in the center is shown below: +
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+ What about for damping? +
++ With a very low damping value, the cloth falls much faster and with more force. A consequence of this is we notice the cloth swinging + back and forth from its pinned points. With a higher damping value, the cloth falls with a lot of resistance to gravity and much more + slowly. The cloth comes to a complete stop with out swinging back and forth – it is much more gentle. +
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+ Show us a screenshot of your shaded cloth from scene/pinned4.json in its final resting state! If you choose to use different parameters + than the default ones, please list them. +
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Part 3: Handling collisions with other objects
++ Show us screenshots of your shaded cloth from scene/sphere.json in its final resting state on the sphere using the + default ks = 5000 as well as with ks = 500 and ks = 50000. Describe the differences in the results. +
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+ Comparing the default final resting state to one where we lower the ks, a lower ks results in less pull from the rest of the + cloth. As a result, other forces are able to have a greater affect on the cloth – in this case, gravity. The ends of the cloth + get pulled down way more. We see the opposite when incerasing the ks. The cloth is less willing to bend to other objects' shapes + and the effect of gravity, and is much more rigid. +
+ ++ Show us a screenshot of your shaded cloth lying peacefully at rest on the plane. If you haven't by now, feel free to express + your colorful creativity with the cloth! (You will need to complete the shaders portion first to show custom colors.) +
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Part 4: Handling self-collisions
++ Show us at least 3 screenshots that document how your cloth falls and folds on itself, starting with an early, initial + self-collision and ending with the cloth at a more restful state (even if it is still slightly bouncy on the ground). +
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+ Vary the density as well as ks and describe with words and screenshots how they affect the + behavior of the cloth as it falls on itself. +
++ Having a lower density causes the cloth to expand more and allows for more distance between each point. A higher + density results in a seemingly stiffer cloth with smaller ripples in it as it is falling. Increasing the ks allows the cloth + to be appear more flowy as it falls on itself. It is not as tightly bound. We have the opposite affect when we decrease the ks. +
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Part 5: Shaders
++Explain in your own words what is a shader program and how vertex and fragment shaders work together to create lighting and material effects. +
++ A shader program is a program that computes shading of vertices and fragments of a scene. + They execute parts of the rasterization pipeline on the GPU in parallel, leading to much faster rendering times. + In order to create lighting and material effects, shader programs compute the shading of the vertex of each fragment (most commonly a triangle) + using different constants, equations, and inputs dependent on the material and intensity and distance of lighting. + The vertex shaders then output aspects of this shading, such as their position and normals. The fragment shaders take these vertices + as input and apply transformations to define how the fragments should be shaded per pixel. When taking the vertices as input, + the shader program automatically linearlly interpolate across all vertices of the fragment, resulting in a smooth per pixel shading. +
++ Explain the Blinn-Phong shading model in your own words. Show a screenshot of your Blinn-Phong shader outputting only the ambient component, + a screen shot only outputting the diffuse component, a screen shot only outputting the specular component, + and one using the entire Blinn-Phong model. +
++ As opposed to the Lambertian/Diffusion shading model, the Blinn-Phong shading model is dependent on view direction. + This means that the lighting and shading of an image will change depending on the camera position where the user is viewing the scene. + The Blinn-Phong shading model combines ambient, diffusion, and specular lighting, where specular lighting is the lighting + dependent on the viewing direction. It calculates the bisecting ray between the camera position and light source to determine the + direction of the viewing angle, namely how similar the viewing angle is to the normal vector. The specular lighting will adjust the + light intensity accordingly, as a viewing angle that is more similar to the normal vector has a greater light intensity. The diffuse + component of the Blinn-Phong model is independent of view direction and calculates the shading of the model by the direction of the + light source relative the vertex position and vertex normal, and the ambient lighting does not depend on anything and adds constant + color depending on how its constants are defined. + +
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+ Show a screenshot of your texture mapping shader using your own custom texture by modifying the textures in /textures/. +
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+ Show a screenshot of bump mapping on the cloth and on the sphere. Show a screenshot of displacement mapping on the sphere. + Use the same texture for both renders. You can either provide your own texture or use one of the ones in the textures directory, + BUT choose one that's not the default texture_2.png. Compare the two approaches and resulting renders in your own words. + Compare how your the two shaders react to the sphere by changing the sphere mesh's coarseness by using -o 16 -a 16 and then -o 128 -a 128. +
++Bump mapping and displacement mapping are both techniques used to relay information of the texture by adjusting the heights of the divots +in the object. Bump mapping does this by changing the lighting of the pixels of the objects, with darker pixels representing divots and +lighter pixels representing peaks (depending on the lighting as well). Displacement also changes the color values of the pixels to represent +height in texture, but it also changes the physical geometry of the object. Comparing bump mapping vs displacement mapping for both the +sphere and the cloth, we can see how bump mapping only changes the color since the sphere remains smooth as it did in our other renders. +With displacement mapping, however, the sphere's geometry changes, as we can see peaks and valleys in the silhouette of the sphere and +the shearing of the texture mapping on the sphere from its geometric change. Comparing the mesh's coarseness with 16x16 vs 128x128 resolution +for the two shaders, the 16x16 resolution results in a render with a smoother sphere face for both shaders, as there is not enough resolution +to capture much of the nuance of the texture mapping applied to the sphere. The displacement mapping differs from the bump mapping in the +16x16 resolution in that the displacement mapping still changes the geometry of the sphere, with edges in its silhouette compared to the +smooth, circular silhouette of the bump mapping. This same difference in geometry and silhouette can be seen between the mapping techniques +in the 128x128 resolution images, but both shaders benefit from the higher resolution, as the face of the sphere captures more of the nuance +of the texture that we applied to it. The face of the sphere has more divots and peaks than the 16x16 rendering, and it is more apparent that +we applied a texture than the 16x16 rendering. +
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+ Show a screenshot of your mirror shader on the cloth and on the sphere. +
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