# How to find paramenters in Surface() function for 3D objects?

Matea Pjanic shared this question 1 year ago

Hello!

Can somebody help me understand how to find the parameters for the Surface() function in 3D?

For example, I need to draw part of sphere, and I use

Surface(cos(x)sin(y), sin(x)sin(y), 2+cos(y), x, 0, pi/2, y, 0, pi/2)

So how to calculate first three parameters of the function?

2

Less elegant but easier to understand is the command Surface(sqrt(1-h²)cos(t), sqrt(1-h²)sin(t), h+2, t, 0°, 90°, h, 0, 1).In this you use the well known parameters cos(t) and sin(t) in a circle. But when z changes, the radius of the circle should change too, so in a right angle triangle Pythagoras gives you the link between the heigth and the radius as sqrt(1-h²) to multiply the expressions for x and y. Result is the same part of a sphere.

chris

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