Obj-Model-Viewer

An interactive 3D OBJ model viewer that supports real-time rendering, Phong illumination, and user-friendly controls.
The viewer automatically centers and scales models (cube, bunny, dragon, Buddha, etc.) for optimal display, with options for rotation, shading, and lighting adjustments.

📸 Preview

✨ Features

• Perspective Projection
  Realistic depth rendering with perspective projection.

• Automatic Centering & Scaling
  Models are centered in the viewport and uniformly scaled to fit the screen.

• Interactive Rotation

  • Spacebar → Toggle continuous rotation
  • Mouse Buttons → Switch rotation axis (X, Y, Z)

• Shading Modes

  • 1 → Phong Shading (smooth shading using vertex normals)
  • 2 → Flat Shading (faceted shading using surface normals)

• Specular Controls

  • 3 / 4 → Increase / decrease specular intensity
  • 5 / 6 → Adjust shininess exponent (highlight size)

🎮 Controls

Key / Mouse	Action
Spacebar	Toggle auto-rotation
Mouse Buttons	Change rotation axis (X, Y, Z)
1	Phong shading
2	Flat shading
3 / 4	Increase / decrease specular intensity
5 / 6	Increase / decrease shininess

⚙️ Implementation Details

1. Model Data

• Models are loaded via MyObj and stored in MyModel instances.
• All faces are treated as triangles.
• Vertex array size = f.size() * 3.

2. Normal Calculation

• Surface Normals

p = b - a
q = c - a
n = p × q

• Vertex Normals
  Accumulated from adjacent faces, averaged and normalized.

3. Model Placement

• Bounding box (min/max coordinates) is computed.
• Largest dimension is used for uniform scaling (to prevent aspect ratio distortion).
• Model is translated to the origin by subtracting its center.

4. Shading & Lighting

Phong illumination model:

I = Lamb * Mamb + Ldiff * Mdiff * (N · L) + Lspec * Mspec * (V · R)^n

🚀 Troubleshooting

• Scaling Distortion
  Initially scaled each axis independently → fixed by scaling uniformly based on the largest dimension.

• Shader Uniform Errors
  Passing isFlat as a float caused issues → fixed with glUniform1i.

• Variable Management
  Careful naming and type consistency were crucial due to many shader uniforms.