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# dribble04

Member Since 06 Oct 2012
Offline Last Active Jun 08 2014 11:42 AM

### Level Of Detail

19 May 2014 - 02:45 AM

Hey, just curious here, but is it possible to have a level of detail for complex models without having their respective LOD models.

Cheers!!

Andre

### Aligning a path, along a another dynamically

09 May 2014 - 05:40 AM

Am building a 2D top down game where there are roads, and intersections, and the user is creating a path, for the car to follow, but that path can be created only on the road, and it has to centre itself on that road. How would I attempt to do this? Am developing in Unity btw.

Right now am gathering the points on input, and based on the direction of the drawn path, it knows if its moving horizontally or vertically, but I am not quite sure how to figure out if its turning. My implementation knows if its turning but it also includes diagonals.

```public void InputUpdate()
{
if(Input.GetMouseButtonDown(0))
{
dragPoints.Clear();
lineRenderer.SetVertexCount(0);

horizontalCount = verticalCount = 0;

isDragging = true;
isComplete = false;
}

if(Input.GetMouseButtonUp(0))
{
isDragging = false;
isComplete = true;
}

if(isDragging)
{
Vector3 tempPosition = gameCamera.ScreenToWorldPoint(Input.mousePosition);
tempPosition = new Vector3(tempPosition.x, tempPosition.y, 0f);

return;

Vector3 totalDirection = Vector3.zero;

int minSamplePoints = 4;

startPoint = dragPoints[0];

if(dragPoints.Count > minSamplePoints)
{
endPoint = dragPoints[dragPoints.Count - 1];

for(int i = 0; i + minSamplePoints < dragPoints.Count; i++)
totalDirection += (dragPoints[i + minSamplePoints] - dragPoints[i]).normalized;

prevAvgX = currentAvgX;
prevAvgY = currentAvgY;

currentAvgX = totalDirection.x / dragPoints.Count;
currentAvgY = totalDirection.y / dragPoints.Count;

if(Mathf.Abs(currentAvgY) <= 0.1f)
{
currentAxis = Axis.Horizontal;
horizontalCount++;
}
else if(Mathf.Abs(currentAvgX) <= 0.1f)
{
currentAxis = Axis.Vertical;
verticalCount++;
}
else
{
if(Mathf.Abs(currentAvgX) > Mathf.Abs(currentAvgY))
currentAxis = Axis.TurnXY;
else if (Mathf.Abs(currentAvgX) < Mathf.Abs(currentAvgY))
currentAxis = Axis.TurnYX;
}
}

RenderLine();
}
}
```

Any help would be much appreciated.

Cheers!!

### Handling time in a physics engine?

23 March 2014 - 11:56 PM

When building a physics engine, how do we handle simulation time, how can it be controlled from system to system (different hardware), how is it maintained? Can you also explain to me the most efficient way to handle frame data, for backtracking and so on.

Cheers!!

### Building a Game Engine

02 December 2013 - 04:16 AM

Hey,

Am planning on trying to build a game engine. Its gonna be an engine that would be refined or built specifically for fighters, and beat em ups. Anyway, I was kinda wondering what are the tools or libraries I may need in conjunction with OpenGL, GLSL, and C++.

- A simpler math library, support for vectors, quaternions, and so on. I have been using GLM, but I'd like to just have header file.

- A sound library, I want to be able to possibly use the pitch and tone, etc to manipulate colors, and lighting.

- A model loader of sorts, support for .obj, .max, etc..

- A GUI library.

Let me know if you know of any that meet the above criteria, and if you think of any other libs or tools that could come in handy please let me know.

Cheers.

### Movement up and down a slope

06 September 2013 - 12:10 AM

Hey, am trying to move an object along a series of slopes, and also make it follow a trajectory when it reaches a certain velocity at the apex of a slope. Am having a few issues with my code. Am coding in C# Unity, so am using Unity's rigid body and collision system, and varying properties as and when required. I would really appreciate it someone could just check and see if there is anything wrong with it.

When I accelerate up a slope, it accelerates but on reaching the top or the apex of the slope it starts to move back down. And when I accelerate down a slope it moves very slowly or doesn't move at all (it should be moving at a greater acceleration).

What is the appropriate condition or process to use to synch all the movement together (such that it is smooth and seamless).

```	public void Accelerate(Vector3 slopeNormal)
{
if(MoveDirection.magnitude > 0f)
{
Vector3 targetVelocity ;
Vector3 currentVelocity ;
Vector3 velocityChange ;
Vector3 force ;
Vector3 a ;

float levelStopTime ;
float brakingDistance ;

targetVelocity = Speed * MoveDirection ;
currentVelocity = Character.rigidbody.velocity;

velocityChange = targetVelocity - currentVelocity;

a.x = Mathf.Clamp(velocityChange.x, -MaxAcceleration, MaxAcceleration);
a.y = Mathf.Clamp(velocityChange.y, -MaxAcceleration, MaxAcceleration);
a.z = Mathf.Clamp(velocityChange.z, -MaxAcceleration, MaxAcceleration);
Acceleration = a.magnitude * Mathf.Pow (Time.deltaTime, 2f);	// Not sure, CHECK!!

force = Character.rigidbody.mass * a ;

//			levelStopTime = (m_character.rigidbody.velocity / m_maxAcceleration).magnitude ;
//			brakingDistance = (m_character.rigidbody.velocity.magnitude * m_levelStopTime) + (m_maxAcceleration * m_levelStopTime) ;//Mathf.Pow(m_levelStopTime, 2f) / 2f) ;

if(Input.GetKey(KeyCode.U))
AccelerateUpSlope(slopeNormal) ;
else if(Input.GetKey(KeyCode.D))
AccelerateDownSlope(slopeNormal) ;
else
}
else
Debug.LogError("Movement Direction Invalid!!") ;
}

public void AccelerateDownSlope(Vector3 slopeNormal)
{
float fG, fNet, fParallel ;
float m ;
float g ;
float theta ;

float a ;
Vector3 A ;

Vector3 characterNormal = Character.rigidbody.velocity.normalized ;

m = Character.rigidbody.mass ;
g = Physics.gravity.y ;

fG = m * g;
theta = Vector3.Angle(characterNormal, slopeNormal) ;

fParallel = fG * Mathf.Sin(theta) ;
fNet = fParallel ;

a = fNet / m ;
A = a * new Vector3(1f, 1f, 0f) ;
Debug.Log("Down " + A) ;

Acceleration = a  * Mathf.Pow (Time.deltaTime, 2f);	// Not sure, CHECK!!
}

public void AccelerateUpSlope(Vector3 slopeNormal)
{
float fG, fNet, fParallel, fPerpendicular ;
float m ;
float g ;
float theta ;

float a ;
Vector3 A ;

Vector3 characterNormal = Character.rigidbody.velocity.normalized ;

m = Character.rigidbody.mass ;
g = Physics.gravity.y ;

fG = m * g;
theta = Vector3.Angle(characterNormal, slopeNormal) ;

Debug.Log(theta) ;

fParallel = fG * Mathf.Sin(theta) ;
fPerpendicular = CoefficentFriction * fG * Mathf.Cos(theta) ;

fNet = fParallel - fPerpendicular ;

a = fNet / m ;
A = a * new Vector3(1f, 1f, 0f) ;
Debug.Log("UP " + A) ;

Acceleration = a  * Mathf.Pow (Time.deltaTime, 2f);	// Not sure, CHECK!!
}

public void ProjectileMotion(Vector3 colliderNormal)
{
float maxVelocityX = 45f ;
float maxVelocityY = 60f ;
Vector3 initialVelocity = go.rigidbody.velocity ;
Vector3 initialPosition = go.rigidbody.position ;

//		float angle = Vector3.Angle(go.rigidbody.position.normalized, colliderNormal) ;
//		float launchAngleRad = (angle * Mathf.PI) / 180f ;

float launchAngleRad = (m_launchAngle * Mathf.PI) / 180f ;
float timeOfFlight = (2f * initialVelocity.magnitude * Mathf.Sin(launchAngleRad)) / Physics.gravity.magnitude ;

//		Debug.Log("Time of Flight - " + timeOfFlight) ;

float x, y ;

x = initialPosition.x + (initialVelocity.x * Mathf.Cos(launchAngleRad) * timeOfFlight) ;
y = initialPosition.y + (initialVelocity.y * Mathf.Sin(launchAngleRad) * timeOfFlight) - (0.5f * Physics.gravity.y * Mathf.Pow(timeOfFlight, 2)) ;

//		Debug.Log("x Position - " + x) ;
//		Debug.Log("y Position - " + y) ;

Vector3 amtToMove = new Vector3(x, y, go.transform.position.z) ;
Vector3 finalVelocity = amtToMove / timeOfFlight ;

//		go.rigidbody.MovePosition(amtToMove) ;

if(finalVelocity.x >= 0f)
{
//			Debug.Log(finalVelocity) ;

finalVelocity.x = Mathf.Clamp(finalVelocity.x, -maxVelocityX, maxVelocityX);
finalVelocity.y = Mathf.Clamp(finalVelocity.y, -maxVelocityY, maxVelocityY);

go.rigidbody.AddForce(finalVelocity, ForceMode.VelocityChange) ;	// ForceMode.Acceleration) ;
}
}
```

Also would this be the best way to check if the object is moving on a slope.

```	public void CollisionCheck(GameObject go)
{
Ray ray ;
RaycastHit hit ;
float x, y ;
//		float offset = 10f ;
float playerGroundSpace = 0.0005f ;

CapsuleCollider collider = go.GetComponent<CapsuleCollider>() ;

// Checking for collision up and down
x = go.transform.position.x - go.transform.localScale.x / 2f ;
y = go.transform.position.y + go.transform.localScale.y / 2f ;

ray = new Ray(new Vector2(x, y), new Vector2(0f, 10f)) ;

Debug.DrawRay(ray.origin, ray.direction);

if (Physics.Raycast(ray, out hit))
{
float dst = Vector3.Distance(ray.origin, hit.point) ;

if(dst > playerGroundSpace)
{
Debug.Log("Collision, UP/DOWN") ;
}
}

// Checking for collision left and right
x = go.transform.position.x + go.transform.localScale.x / 2f ;
y = go.transform.position.y - go.transform.localScale.y / 2f ;

ray = new Ray(new Vector2(x, y), new Vector2(10, 0)) ;

Debug.DrawRay(ray.origin, ray.direction);

if (Physics.Raycast(ray, out hit))
{
float dst = Vector3.Distance(ray.origin, hit.point) ;

if(dst > playerGroundSpace)
{
Debug.Log("Collision, LEFT/RIGHT") ;
}
}
}
```

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