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Search found 4 results on 1 pages for 'manning18'.

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• Question about Target parameter of Matrix.CreateLookAt

  - by manning18

  I have a newbie question that's causing me a little bit of confusion when experimenting with cameras and reading other peoples implementations - does this parameter represent a point or a vector? In some examples I've seen people treat it like a specific point they are looking at (eg a position in the world), other times I see people caching the orientation of the camera in a rotation matrix and simply using the Matrix.Forward property as the "target", and other times it's a vector that's the result of targetPos - camPos and also I saw a camPos + orientation.Forward I was also just playing around with hard-coded target positions with same direction eg 1 to 10000 with no discernible difference in what I saw in the scene. Is the "Target" parameter actually a position or a direction (irrespective of magnitude)? Are there any subtle differences in behaviors, common mistakes or gotchas that are associated with what values you provide, or HOW you provide this paramter? Are all the methods I mentioned above equivalent? (sorry, I've only recently started and my math is still catching up)

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• Why does multiplying texture coordinates scale the texture?

  - by manning18

  I'm having trouble visualizing this geometrically - why is it that multiplying the U,V coordinates of a texture coordinate has the effect of scaling that texture by that factor? eg if you scaled the texture coordinates by a factor of 3 ..then doesn't this mean that if you had texture coordinates 0,1 and 0,2 ...you'd be sampling 0,3 and 0,6 in the U,V texture space of 0..1? How does that make it bigger eg HLSL: tex2D(textureSampler, TexCoords*3) Integers make it smaller, decimals make it bigger I mean I understand intuitively if you added to the U,V coordinates, as that is simply an offset into the sampling range, but what's the case with multiplication? I have a feeling when someone explains this to me I'm going to be feeling mighty stupid

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• SpriteBatch.Begin() making my model not render correctly

  - by manning18

  I was trying to output some debug information using DrawString when I noticed my model suddenly was being rendered like it was inside-out (like the culling had been disabled or something) and the texture maps weren't applied I commented out the DrawString method until I only had SpriteBatch.Begin() and .End() and that was enough to cause the model rendering corruption - when I commented those calls out the model rendered correctly What could this be a symptom of? I've stripped it down to the barest of code to isolate the problem and this is what I noticed. Draw code below (as stripped down as possible) GraphicsDevice.Clear(Color.LightGray); foreach (ModelMesh mesh in TIEAdvanced.Meshes) { foreach (Effect effect in mesh.Effects) { if (effect is BasicEffect) ((BasicEffect)effect).EnableDefaultLighting(); effect.CurrentTechnique.Passes[0].Apply(); } } spriteBatch.Begin(); spriteBatch.DrawString(spriteFont, "Camera Position: " + cameraPosition.ToString(), new Vector2(10, 10), Color.Blue); spriteBatch.End(); GraphicsDevice.DepthStencilState = DepthStencilState.Default; TIEAdvanced.Draw(Matrix.CreateScale(0.025f), viewMatrix, projectionMatrix);

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• When to use Euler vs Axis angles vs Quaternions?

  - by manning18

  I understand the theory behind each but I was wondering if people could share their experiences in when one would use one over the other For instance, if you were implementing a chase camera, a FPS-style mouse look or writing some kinematic routine, what would be the factors you consider to go with one type over the other and when might you need to convert from one form of representation to the other? Are there certain things that only one system can do that the others can't? (eg smooth interpolation with quaternions)

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